Coelenterazine analogues and coelenteramide analogues

ABSTRACT

Coelenterazine analogues with different luminescence properties from conventional ones and coelenteramide analogues with different fluorescence properties from conventional ones have been desired. The invention provides coelenterazine analogues modified at the 8-position of coelenterazine and coelenteramide analogues modified at the 2- or 3-position of coelenteramide.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of Japanese patent application no. 2010-088175, filed on Apr. 6, 2010 under 35 U.S.C. §119, and is incorporated by reference herein in its entirety.

REFERENCE TO A SEQUENCE LISTING

A Sequence Listing containing SEQ ID NOS. 1-12 is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to coelenterazine analogue, coelenteramide analogue, calcium-binding photoprotein, fluorescent protein, and the like.

BACKGROUND ART

A calcium-binding photoprotein is one of the proteins responsible for bioluminescence. This photoprotein emits light upon specific interaction with Ca²⁺. The calcium-binding photoprotein is a complex of a protein having the catalytic function of oxygenation and a peroxide of luciferin as a light emitting substrate. In the calcium-binding photoprotein, the protein having the catalytic function of oxygenation refers to as an apoprotein. The peroxide of a luciferin is coelenterazine peroxide (2-hydroperoxycoelenterazine). The calcium-binding photoprotein including aequorin, clytin-I, clytin-II, mitrocomin, obelin, etc. are known and present in coelenterates. Among these photoproteins, aequorin is a photoprotein isolated from the luminous jellyfish Aequorea aequorea (1: Shimomura, In: Bioluminescence, Chemical Principles and Methods, (2006) pp 90-158, World Scientific Pub. Co.; 2: Shimomura et al., (1962) J. Cell. Comp. Physiol. 59, pp 223-240). Aequorin is a non-covalent complex of apoaequorin (21.4 kDa), which is an apoprotein, and a hydroperoxide of coelenterazine (3: Head et al., (2000) Nature, 405 372-376). Apoaequorin is composed of 189 amino acid residues in a single polypeptide chain and has three EF-hand motifs characteristic of Ca²⁺-binding sites (4: Inouye et al., (1985) Proc. Natl. Acad. Sci. USA. 82, 3154-3158). In the presence of Ca²⁺, aequorin emits blue light (λ_(max)=˜460 nm) by an intramolecular reaction and decomposes itself into apoaequorin, coelenteramide and CO₂ (5: Shimomura & Johnson (1972) Biochemistry 11, 1602-1608.; 6: Shimomura & Johnson (1973) Tetrahedron Lett. 2963-2966). The complex of Ca²⁺-binding apoaequorin with coelenteramide obtained by this decomposition is known as blue fluorescent protein (BFP) (7: Shimomura & Johnson (1975) Nature 256, 236-238). The fluorescence and luminescence spectra of this BFP are identical to the bioluminescence spectra of aequorin (8: Shimomura (1995) Biochem. J. 306, 537-543; 9: Inouye (2004) FEBS Lett. 577, 105-110).

Recombinant aequorin can be obtained by incubating recombinant apoaequorin prepared from Escherichia coli with coelenterazine in the presence of EDTA and a reducing reagent (10: Inouye et al. (1986) Biochemistry 25, 8425-8429; 11: Inouye et al. (1989) J. Biochem. 105, 473-477). This recombinant aequorin is highly purified (12: Shimomura & Inouye (1999) Protein Express. Purif. 16, 91-95). The luminescence properties of recombinant aequorin are identical to that of native aequorin (13: Shimomura et al. (1990) Biochem. J. 270, 309-312).

Approximately 50 types of coelenterazine analogues (CTZ analogues) were hitherto synthesized and some of them were actually used to prepare semi-synthetic aequorins (e.g., 13: Shimomura et al. (1990) Biochem. J. 270, 309-312, 14: Shimomura O. et al. (1988) Biochem. J. 251, 405-410, 15: Shimomura O. et al. (1989) Biochem. J. 261, 913-920, 16: Inouye S. & Shimomura O. (1997) Biochem. Biophys. Res. Commun. 233, 349-353).

The crystal structures of aequorin and semi-synthetic aequorins have been determined (3: Head et al. (2000) Nature 405, 372-376; 17: Toma et al. (2005) Protein Science 14, 409-416), and the binding properties of Mg²⁺ to EF-hand motif of aequorin were also investigated by NMR analysis (18: Ohashi et al. (2005) 1 J. Biochem. 38, 613-620).

Recently, BFP was quantitatively prepared from the purified recombinant aequorin (9: Inouye, FEBS Lett. 577 (2004) 105-110; 19: Inouye & Sasaki, FEBS Lett. 580 (2006) 1977-1982). BFP was found to have a substantial luminescence activity, catalyzing the oxidation of coelenterazine like a luciferase. The luminescence activity of BFP is about 10 times higher than that of Ca²⁺-binding apoaequorin (9: Inouye, FEBS Lett. 577 (2004) 105-110). Thus, BFP is a novel bifunctional protein having both fluorescence and luciferase activities. BFP is further converted into green fluorescent protein (gFP) having the fluorescence emission maximum peak at around 470 nm by the treatment of EDTA.

gFP is a non-covalent complex of apoaequorin with coelenteramide and aequorin can be obtained by incubation of gFP with coelenterazine at 25° C. in the absence of a reducing reagent (9: Inouye (2004) FEBS Lett. 577, 105-110). By incubation of BFP or gFP with various coelenterazine analogues in the presence of EDTA and dithiothreitol (DTT), semi-synthetic aequorins could be also prepared (19: Inouye & Sasaki (2006) FEBS Lett. 580, 1977-1982). Furthermore, the luminescence activity of BFP as a luciferase is stimulated by the addition of imidazole at the concentrations of 30 to 300 mM using coelenterazine and its analogue as a substrate (20: Inouye & Sasaki (2007) Biochem. Biophys. Res. Commun. 354, 650-655).

In the development of use of BFP and gFP, there are some problems that the catalytic domain for oxygenation of coelenterazine, which is important basic information, or amino acid residues in BFP and gFP still remain to be elucidated. In order to solve these problems and in the development of use, it is necessary to easily prepare several tens milligrams of BFP and gFP and succeed. The present inventors have also established a method for preparing semi-synthetic gFP and semi-synthetic BFP from apoaequorin and chemically synthesized coelenteramide (21: Inouye & Hosoya (2009) Biochem. Biophys. Res. Commun. 386, 617-622). Semi-synthetic BFP prepared by this method shows a luciferase activity using coelenterazine as a substrate, similar to BFP prepared from aequorin by Ca2+-triggered luminescence reaction. The emission spectrum of semi-synthetic BFP is blue with around 470 nm.

When/As an in vivo probe to be used, a probe having the maximum wavelength of fluorescence closer to that of the near infrared region (longer than 600 nm) has been desired. In semi-synthetic BFP and semi-synthetic gFP prepared from coelenteramide analogues and apoaequorin from native aequorin, however, those having a maximum wavelength of fluorescence at 485 nm or longer have not yet been reported.

References

-   1: Shimomura, In: Bioluminescence, Chemical principles and     methods (2006) pp 90-158, World Scientific Pub. Co. -   2: Shimomura et al. (1962) J. Cell. Comp. Physiol. 59, 223-240 -   3: Head et al. (2000) Nature 405, 372-376 -   4: Inouye et al. (1985) Proc. Natl. Acad. Sci. USA. 82, 3154-3158 -   5: Shimomura & Johnson (1972) Biochemistry 11, 1602-1608 -   6: Shimomura & Johnson (1973) Tetrahedron Lett. 2963-2966 -   7: Shimomura & Johnson (1975) Nature 256, 236-238 -   8: Shimomura (1995) Biochem. J. 306, 537-543 -   9: Inouye (2004) FEBS Lett. 577, 105-110 -   10: Inouye et al (1986) Biochemistry 25, 8425-8429 -   11: Inouye et al. (1989) J. Biochem. 105 473-477 -   12: Shimomura & Inouye (1999) Protein Express. Purif. 16, 91-95 -   13: Shimomura et al. (1990) Biochem. J. 270, 309-312 -   14: Shimomura et al. (1988) Biochem. J. 251, 405-410 -   15: Shimomura et al. (1989) Biochem. J. 261, 913-920 -   16: Inouye S. & Shimomura O. (1997) Biochem. Biophys. Res. Commun.     233, 349-353 -   17: Toma et al. (2005) Protein Science 14, 409-416 -   18: Ohashi et al. (2005) J. Biochem. 138, 613-620 -   19: Inouye & Sasaki (2006) FEBS Lett. 580, 1977-1982 -   20: Inouye & Sasaki (2007) Biochem. Biophys. Res. Commun. 354,     650-655 -   21: Inouye & Hosoya (2009) Biochem. Biophys. Res. Commun. 386,     617-622

DISCLOSURE OF INVENTION

Under the foregoing circumstances, coelenterazine analogues showing different luminescence properties from conventional ones have also been desired.

Furthermore, coelenteramide analogues showing different fluorescence properties from conventional ones and fluorescent proteins containing such coelenteramide analogues have been desired.

In order to solve the above problems, the present inventors have made extensive investigations and, as a result, have found that coelenterazine analogues modified at the 8-position of coelenterazine show different luminescence properties from those of known compounds, that coelenteramide analogues modified at the 2- or 3-position of coelenteramide show different luminescence properties from those of known compounds, and so on. Thus, the present invention has come to be accomplished.

The present invention provides the following coelenterazine analogues, coelenteramide analogues, calcium-binding photoproteins, fluorescent proteins, and so on.

[1] A compound represented by general formula (I) shown below:

wherein R³ is hydrogen atom, bromine atom and any one selected from the groups represented by formulas below:

wherein each of R⁶, R⁷ and R⁸ independently represents hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R⁶ and R⁸ may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R⁶ and R⁸.

[2] The compound according to [1] above, which is selected from the compounds shown below.

[3] The compound according to [1] above, which is selected from the compounds shown below.

[4] A compound represented by general formula (II) below:

wherein R^(3′) is hydrogen atom, bromine atom and any one selected from the groups represented by formulas below:

wherein each of R^(6′), R^(7′) and R^(8′) independently represents hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R^(6′) and R^(8′) may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R^(6′) and R^(8′).

[5] The compound according to [4] above, which is selected from the compounds shown below.

[6] A compound represented by general formula (III) below:

wherein Z¹ is O or S; and R^(3″) is hydrogen atom, bromine atom, a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, a substituted or unsubstituted arylalkenyl, a substituted or unsubstituted arylalkynyl, an alkyl which may optionally be substituted with an alicyclic group, an alkenyl which may optionally be substituted with an alicyclic group, an alkynyl which may optionally be substituted with an alicyclic group, an alicyclic group, or a heterocyclic group.

[7] A compound represented by general formula (IV) below:

wherein R^(2″′) is a group selected from the groups shown below:

and R^(3″′) is hydrogen atom, bromine atom, a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, a substituted or unsubstituted arylalkenyl, a substituted or unsubstituted arylalkynyl, an alkyl which may optionally be substituted with an alicyclic group, an alkenyl which may optionally be substituted with an alicyclic group, an alkynyl which may optionally be substituted with an alicyclic group, an alicyclic group, or a heterocyclic group.

[8] The compound according to [6] or [7] above, which is selected from the compounds shown below.

[9] A calcium-binding photoprotein comprising a peroxide of the compound according to any one of [1] to [3] above and an apoprotein of a calcium-binding photoprotein.

[10] A process for producing a calcium-binding photoprotein, which comprises contacting the compound according to any one of [1] to [3] above with an apoprotein of a calcium-binding photoprotein to obtain the calcium-binding photoprotein.

[11] A method for detecting or quantifying calcium ions, which comprises using the calcium-binding photoprotein according to [9] above.

[12] A method for analyzing a physiological function or enzyme activity, which comprises performing the bioluminescence resonance energy transfer (BRET) method using the calcium-binding photoprotein according to [9] above as a donor protein.

[13] A fluorescent protein comprising the compound according to any one of [4] to [8] above, an apoprotein of a calcium-binding photoprotein and calcium ions or divalent or trivalent ions replaceable for the calcium ions.

[14] A method for producing a fluorescent protein, which comprises contacting the calcium-binding photoprotein according to [9] above with calcium ions or divalent or trivalent ions replaceable for the calcium ions to obtain the fluorescent protein.

[15] A method for producing a fluorescent protein, which comprises contacting the compound according to any one of [4] to [8] above with an apoprotein of a calcium-binding photoprotein in the presence of calcium ions or divalent or trivalent ions replaceable for the calcium ions to obtain the fluorescent protein.

[16] The method according to [14] or [15] above, wherein the contact is carried out in the presence of a reducing agent.

[17] A fluorescent protein comprising the compound according to any one of [4] to [8] above and an apoprotein of a calcium-binding photoprotein.

[18] A method for producing a fluorescent protein, which comprises contacting the compound according to any one of [4] to [8] above with an apoprotein of a calcium-binding photoprotein in the presence of a chelating agent for removing calcium ions or divalent or trivalent ions replaceable for the calcium ions to obtain the fluorescent protein.

[19] A method for producing a fluorescent protein, which comprises treating the fluorescent protein according to [13] above with a chelating agent for removing calcium ions or divalent or trivalent ions replaceable for the calcium ions.

[20] The method according to [18] or [19] above, wherein the contact is carried out in the presence of a reducing agent.

[21] A method for analyzing a physiological function or enzyme activity, which comprises performing the fluorescence resonance energy transfer (FRET) method using the fluorescent protein according to [13] or [17] above as an acceptor or a donor.

According to the present invention, a novel coelenterazine analogue is provided. Coelenterazine analogues in some embodiments of the present invention show different luminescence properties from those of known coelenterazine.

According to the present invention, a novel coelenteramide analogue is provided. Coelenteramide analogues in some embodiments of the present invention show different fluorescence properties from those of known coelenteramide.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

FIG. 1 shows the luminescence spectra of semi-synthetic aequorins prepared from coelenterazine analogues by addition of calcium.

FIG. 2 shows the fluorescence spectra of fluorescent proteins obtained by adding calcium inos to semi-synthetic aequorins prepared from coelenterazine analogues.

FIG. 3 shows the relationship between the initial luminescence intensities of semi-synthetic aequorins and various concentrations of calcium ion.

FIG. 4 shows the fluorescence spectra of semi-synthetic gFP prepared from coelenteramide analogues (4a to 4l) and apoaequorin in the presence of EDTA.

FIG. 5 shows the fluorescence spectra of semi-synthetic gFP prepared from coelenteramide analogues (4m to 4z) and apoaequorin in the presence of EDTA.

FIG. 6 shows the fluorescence spectra of semi-synthetic BFP prepared from coelenteramide analogues (4a to 4l) and apoaequorin in the presence of calcium ions.

FIG. 7 shows the fluorescence spectra of semi-synthetic BFP prepared from coelenteramide analogues (4m to 4z) and apoaequorin in the presence of calcium ions.

FIG. 8 shows the scheme for preparing BFP, gFP, aequorin, etc. from coelenteramide.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention is described in detail.

1. Coelenterazine Analogues of the Invention

The present invention provides the compounds represented by general formula (I) (sometimes referred to as the “coelenterazine analogues of the present invention”). Coelenterazine analogues are modified at the C-8 position of coelenterazine.

(wherein R³ is hydrogen atom, bromine atom and any one selected from the groups represented by formulas below:

wherein each of R⁶, R⁷ and R⁸ independently represents hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R⁶ and R⁸ may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R⁶ and R⁸).

As used herein, the “substituted or unsubstituted alkyl having 1 to 6 carbon atoms” shown by R⁶, R⁷ and R⁸ is, for example, an alkyl having 1 to 6 carbon atoms and carrying 1 to 5 substituents which may be the same or different, or an unsubstituted alkyl. Examples of the substituent include at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isopropoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. The “substituted or unsubstituted alkyl having 1 to 6 carbon atoms” is methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl, fluoromethyl, a perfluoroalkyl (e.g., trifluoromethyl, perfluorohexyl), or the like.

The “substituted or unsubstituted aryl” shown by R⁶, R⁷ and R⁸ or the “substituted or unsubstituted aryl” formed by combining R⁶ and R⁸ together with the carbon atom bound to each of R⁶ and R⁸ is, for example, an aryl having 1 to 5 substituents, which are the same or different, or an unsubstituted aryl. The substituent includes, for example, at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. In some embodiments of the present invention, the substituent includes hydroxy group, nitro or dimethylamino. The “substituted or unsubstituted aryl” specifically includes phenyl, a naphthyl (1-naphthyl, 2-naphthyl), a hydroxyphenyl (2-hydroxyphenyl, 3-hydroxyphenyl, 4-hydroxyphenyl), an aminophenyl (e.g., 4-dimethylaminophenyl), a nitrophenyl (e.g., 4-nitrophenyl), a fluorophenyl (e.g., 4-fluorophenyl), a trifluoromethylphenyl (e.g., 4-trifluoromethylphenyl), and the like.

The “substituted or unsubstituted heteroaryl” shown by R⁶, R⁷ and R⁸ or the “substituted or unsubstituted heteroaryl” formed by combining R⁶ and R⁸ together with the carbon atom bound to each of R⁶ and R⁸ is, for example, a heteroaryl having 1 to 5 substituents, which are the same or different, or an unsubstituted heteroaryl. The substituent includes, for example, at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl and 1-pyrrolidinyl, preferably, dimethylamino, diethylamino, ethylmethylamino and diisopropylamino), an aryl (e.g., phenyl, naphthyl, anthranyl), a heteroaryl (e.g., a thienyl (2-thienyl, 3-thienyl), a furyl (2-furyl, 3-furyl), a pyrrolyl (2-pyrrolyl, 3-pyrrolyl), a pyridyl (2-pyridyl, 3-pyridyl, 4-pyridyl), imidazoyl, pyrazoyl, oxazoyl, thiazoyl, isoxazoyl, pyrimidyl, pyrazyl, pyridazoyl), and the like. Specifically, the “substituted or unsubstituted heteroaryl” is a thienyl (2-thienyl, 3-thienyl), a benzothienyl (e.g., benzo[b]thiophen-2-yl, benzo[b]thiophen-3-yl), a thienothienyl (e.g., thieno[2,3-b]thienyl, thieno[3,2-b]-thienyl, thieno[3,2-b:2,3-d]thienyl), a bithiophenyl (e.g., 2,2-bithiophen-5-yl), benzofuranyl, indoyl, indazoyl, benzimidazoyl, benzoxazoyl, benzisoxazoyl, quinolinyl, isoquinolinyl, quinoxalinyl, quinazolinyl, acridinyl, or the like.

In a preferred embodiment of the present invention, coelenterazine analogue includes the following compounds.

In a more preferred embodiment of the present invention, coelenterazine analogue includes the following compounds.

The calcium-binding photoprotein which contains some coelenterazine analogues of the present invention as a light emitting substrate provides a longer half decay time of luminescence, which is a time period in which the luminescence becomes half of the maximum luminescence intensity, when compared to a photoprotein containing coelenterazine as a light emitting substrate. For example, the half decay time is longer by 1.1 times or more, 1.2 times or more, 1.3 times or more, 1.4 times or more, 1.5 times or more, 2.0 times or more, 3.0 times or more, 4.0 times or more, 5.0 times or more, 10 times or more, 15 times or more, 20 times or more, 30 times or more, 40 times or more, 50 times or more, 60 times or more, or 70 times or more. More specifically, coelenterazine analogues, which can provide a longer half decay time of luminescence than that of coelenterazine, are 3a, 3b, 3d, 3e, 3f, 3h and 3j, preferably 3a, 3e, 3f and 3j and more preferably 3f, in coelenterazine analogues (3a to 3t).

The calcium-binding photoprotein which contains some more coelenterazine analogues of the present invention as a light emitting substrate gives different luminescence spectra, unlike fluorescence spectra of the corresponding fluorescent protein prepared by generating luminescence of the calcium-binding photoprotein by addition of calcium. For example, the maximum emission wavelength between the luminescence and the fluorescence is different by ±20 nm or more, ±25 nm or more, ±30 nm or more, ±35 nm or more, ±40 nm or more, ±45 nm or more, ±50 nm or more, ±60 nm or more, ±70 nm or more, ±80 nm or more, ±90 nm or more, ±100 nm or more, ±110 nm or more, ±120 nm or more, or ±130 nm. More specifically, coelenterazine analogues, which can provide different luminescence spectra and fluorescence spectra, are 3a, 3b, 3e, 3f, 3h and 3j, preferably 3a, 3e and 3j and more preferably 3b and 3j, in coelenterazine analogues (3a to 3t).

2. Method for Producing Coelenterazine Analogue of the Invention

Coelenterazine analogue of the present invention described above, i.e., coelenterazine analogue represented by general formula (I) below:

(wherein R³ is the same as defined above) can be produced as follows. That is, coelenterazine analogue represented by general formula (I) can be obtained by reacting a compound represented by general formula (I-1) below:

(wherein R³ is the same as defined above and Y¹ is hydrogen atom or a protecting group) with a compound represented by general formula (I-2) below:

(wherein Y² is hydrogen atom or a protecting group, R² is independently methyl, ethyl, propyl, butyl or isopropyl, and two R² may be combined together to form an alkylene having 2 to 4 carbon atoms). Thus, the compound represented by general formula (I) can be obtained.

As used herein, the protecting groups shown by Y¹ and Y² independently represent, e.g., tert-butyldimethylsilyl (TBDMS), text-butyldiphenylsilyl (TBDPS), trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), methoxymethyl (MOM), 2-methoxethoxyymethyl (MEM), 2-tetrahydropyranyl (THP), etc., particularly preferably TBDMS, MOM or THP.

The alkylene having 2 to 4 carbon atoms, which are formed by combining two R² together, includes ethylene, propylene, butylene, etc.

The compound represented by general formula (I-1) can be produced by known methods. For example, the compound represented by general formula (I-1) can be produced by, for example, the methods described in Y. Kishi et al., Tetrahedron Lett., 13, 2747-2748 (1972), M. Adamczyk et al., Org. Prep. Proced. Int, 33, 477-485 (2001) or F. D. Wael et al., Bioorg. Med. Chem., 17, 4336-4344 (2009), or modifications of these methods. More specifically, the compound represented by general formula (I-1) can be produced as follows. First, cyclization of a substituted phenylglyoxal aldoxime and a glycinonitrile derivative is carried out to form the pyrazine oxide. Subsequently, the pyrazine oxide is subjected to catalytic hydrogenation using Raney Ni, etc. as a catalyst to produce the compound. Alternatively, the compound can be produced either by the Suzuki-Miyaura coupling reaction of a 2-amino-5-bromopyrazine derivative having a suitable substituent at the 3-position and a substituted phenyl borate or a substituted pinacol borate ester, or by the Suzuki-Miyaura coupling reaction of a 2-amino-5-bromopyrazine derivative and a suitable boric acid derivative or a pinacol borate ester.

The compound represented by general formula (I-2) can be produced by known methods. For example, the compound represented by general formula (I-2) can be produced by, for example, the methods described in M. Adamczyk, M. et al., Synth. Commun., 32, 3199-3205 (2002) or H. Baganz & H.-J. May, Chem. Ber, 99, 3766-3770 (1966) and H. Baganz & H.-J. May, Angew. Chem. Mt. Ed. Eng., 5, 420 (1966), or modifications of these methods. More specifically, the compound represented by general formula (I-2) can be produced by reacting a substituted benzyl Grignard reagent with ethyl diethoxyacetate at a low temperature (−78° C.), or by reacting an α-diazo-α-substituted phenyl ketone with tert-butyl hypochlorite in ethanol.

As used herein, the reagent used in the method for producing the compound of the present invention represented by general formula (I) is an acid catalyst such as hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, perchloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, etc. These reagents may be used alone or as a mixture thereof; hydrochloric acid is particularly preferred.

The solvent used in the method for producing the compound of the present invention represented by general formula (I) is not particularly limited, but various solvents can be used. Examples of the solvent are dioxane, tetrahydrofuran, ether, methanol, ethanol, water, etc., which can be used alone or as a mixture thereof.

In the method for producing the compound of the present invention represented by general formula (I), the reaction temperature and reaction time are not particularly limited but are generally at 0° C. to 200° C. for 1 to 96 hours, at room temperature to 150° C. for 3 to 72 hours, or at 60° C. to 120° C. for 6 to 24 hours.

3. Coelenteramide Analogue of the Invention

The present invention provides the compound represented by general formula (II) or general formula (III) below (hereinafter sometimes referred to as “coelenteramide analogue of the present invention”). Coelenteramide analogue of the present invention is modified at the C-3 or C-2 position of coelenteramide.

3.1. Coelenteramide Analogue Modified at the C-3 Position

Coelenteramide analogue of the present invention, which is modified at the 3-position, includes the following compounds.

(wherein R^(3′) is hydrogen atom, bromine atom and any one selected from the groups represented by formulas below:

wherein each of R^(6′), R^(7′) and R^(8′) independently represents hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R^(6′) and R^(8′) may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R^(6′) and R^(8′)).

As used herein, the “substituted or unsubstituted alkyl having 1 to 6 carbon atoms” shown by R^(6′), R^(7′) and R^(8′) is, for example, an alkyl having 1 to 6 carbon atoms and carrying 1 to 5 substituents which are the same or different, or an unsubstituted alkyl. Examples of the substituent include at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. The “substituted or unsubstituted alkyl having 1 to 6 carbon atoms” is methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl, fluoromethyl, a perfluoroalkyl (e.g., trifluoromethyl, perfluorohexyl), or the like.

As used herein, the “substituted or unsubstituted aryl” shown by R^(6′), R^(7′) and R^(8′) or the “substituted or unsubstituted aryl” formed by combining R^(6′) and R^(8′) together with the carbon atom bound to each of R^(6′) and R^(8′) is, for example, an aryl having 1 to 5 substituents which are the same or different, or an unsubstituted aryl. Examples of the substituent include at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl) and the like. In some embodiments of the present invention, the substituent is hydroxy group, nitro or dimethylamino. Specifically, the “substituted or unsubstituted aryl” includes phenyl, a naphthyl (1-naphthyl, 2-naphthyl), a hydroxyphenyl (2-hydroxyphenyl, 3-hydroxyphenyl, 4-hydroxyphenyl), an aminophenyl (e.g., 4-dimethylaminophenyl), a nitrophenyl (e.g., 4-nitrophenyl), a fluorophenyl (e.g., 4-fluorophenyl), a trifluoromethylphenyl (e.g., 4-trifluoromethylphenyl), etc.

The “substituted or unsubstituted heteroaryl” shown by R^(6′), R^(7′) and R^(8′) or the “substituted or unsubstituted heteroaryl” formed by combining R^(6′) and R^(8′) together with the carbon atom bound to each of R^(6′) and R^(8′) is, for example, a heteroaryl having 1 to 5 substituents which are the same or different, or an unsubstituted heteroaryl. Examples of the substituent include at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl and 1-pyrrolidinyl, preferably, dimethylamino, diethylamino, ethylmethylamino, diisopropylamino), an aryl (e.g., phenyl, naphthyl, anthranyl), a heteroaryl (e.g., a thienyl (2-thienyl, 3-thienyl), a furyl (2-furyl, 3-furyl), a pyrrolyl (2-pyrrolyl, 3-pyrrolyl), a pyridyl (2-pyridyl, 3-pyridyl, 4-pyridyl), imidazoyl, pyrazoyl, oxazoyl, thiazoyl, isoxazoyl, pyrimidyl, pyrazyl, pyridazoyl) and the like. Specifically, the “substituted or unsubstituted heteroaryl” is a thienyl (2-thienyl, 3-thienyl), a benzothienyl (e.g., benzo[b]thiophen-2-yl, benzo[b]thiophen-3-yl), a thienothienyl (e.g., thieno[2,3-b]thienyl, thieno[3,2-b]thienyl, thieno[3,2-b:2,3-d]thienyl), a bithiophenyl (e.g., 2,2-bithiophen-5-yl), benzofuranyl, indoyl, indazoyl, benzimidazoyl, benzoxazoyl, benzisoxazoyl, quinolinyl, isoquinolinyl, quinoxalinyl, quinazolinyl, acridinyl, etc.

In a preferred embodiment of the present invention, coelenteramide analogue modified at the C-3 position includes the following compounds.

3.2. Coelenteramide Analogue Modified at the C-2 Position

Coelenteramide analogue in some embodiments of the present invention, which is modified at the C-2-position, includes the following compounds.

(wherein Z¹ is O or S; and R^(3″) is hydrogen atom, bromine atom, a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, a substituted or unsubstituted arylalkenyl, a substituted or unsubstituted arylalkynyl, an alkyl which may optionally be substituted with an alicyclic group, an alkenyl which may optionally be substituted with an alicyclic group, an alkynyl which may optionally be substituted with an alicyclic group, an alicyclic group, or a heterocyclic group.)

As used herein, the “substituted or unsubstituted aryl” shown by R^(3″) is, for example, an aryl having 1 to 5 substituents, or an unsubstituted aryl. For example, the substituted or unsubstituted aryl is at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), amino, a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. In some embodiments of the present invention, the substituent is hydroxy group. Specifically, the “substituted or unsubstituted aryl” is phenyl, p-hydroxyphenyl, p-aminophenyl, p-dimethylaminophenyl, or the like, preferably phenyl, p-hydroxyphenyl, etc. In some embodiments of the present invention, the “substituted or unsubstituted aryl” is an unsubstituted aryl, e.g., phenyl, etc.

The “substituted or unsubstituted arylalkyl” shown by R^(3″) is, for example, an arylalkyl having 7 to 10 carbon atoms and carrying 1 to 5 substituents, or an unsubstituted arylalkyl having 7 to 10 carbon atoms. Examples of the substituents include a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), amino, a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. The “substituted or unsubstituted arylalkyl” includes, for example, benzyl, α-hydroxybenzyl, phenylethyl, p-hydroxybenzyl, p-dimethylaminobenzyl, etc., preferably benzyl, α-hydroxybenzyl, phenylethyl, etc. In some embodiments of the present invention, the “substituted or unsubstituted arylalkyl” is benzyl.

The “substituted or unsubstituted arylalkenyl” shown by R^(3″) is, for example, an arylalkenyl having 8 to 10 carbon atoms and carrying 1 to 5 substituents, or an unsubstituted arylalkenyl having 8 to 10 carbon atoms. Examples of the substituents include a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), amino, a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. For example, the “substituted or unsubstituted arylalkenyl” is phenylvinyl, p-hydroxyphenylvinyl, or p-dimethylaminophenylvinyl. In some embodiments of the present invention, the “substituted or unsubstituted arylalkenyl” is an unsubstituted arylalkenyl, e.g., phenylvinyl.

The “substituted or unsubstituted arylalknyl” shown by R^(3″) is, for example, an arylalknyl having 8 to 10 carbon atoms and carrying 1 to 5 substituents, or an unsubstituted arylalknyl having 8 to 10 carbon atoms. Examples of the substituents include a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), amino, a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), and the like. Examples of the “substituted or unsubstituted arylalknyl” are phenylethynyl, naphthylethynyl, 4-fluorophenylethynyl, 4-trifluoromethylphenylethynyl, 4-methoxyphenylethynyl, 4-nitrophenylethynyl, etc., preferably, phenylethynyl, etc.

The “alkyl which may optionally be substituted with an alicyclic group” shown by R^(3″) is, for example, an unsubstituted straight or branched alkyl having 1 to 4 carbon atoms, or a straight or branched alkyl having 1 to 4 carbon atoms, which is substituted with an alicyclic group having, e.g., 1 to 10 carbon atoms. Examples of the alicyclic group include cyclohexyl, cyclopentyl, adamantyl, cyclobutyl, cyclopropyl, and the like. Preferably, the alicyclic group is cyclohexyl, cyclopentyl or adamantyl. Examples of the “alkyl which may optionally be substituted with an alicyclic group” are methyl, ethyl, propyl, 2-methylpropyl, adamantylmethyl, cyclopentylmethyl, cyclohexylmethyl, cyclohexylethyl, cyclobutylmethyl, cyclopropylmethyl, or the like, preferably, methyl, ethyl, propyl, 2-methylpropyl, adamantylmethyl, cyclopentylmethyl, cyclohexylmethyl, cyclohexylethyl, etc. In some embodiments of the present invention, the “alkyl which may optionally be substituted with an alicyclic group” is a straight alkyl which may optionally be substituted with an alicyclic group, for example, methyl, ethyl, propyl, adamantylmethyl, cyclopentylmethyl, cyclohexylmethyl, cyclohexylethyl, etc.

The “alkenyl which may optionally be substituted with an alicyclic group” shown by R^(3″) is, for example, an unsubstituted straight or branched alkenyl having 2 to 6 carbon atoms, or a straight or branched alkenyl having 2 to 6 carbon atoms, which is substituted with an alicyclic group having, e.g., 1 to 10 carbon atoms. Examples of the alicyclic group include cyclohexyl, cyclopentyl, adamantyl, cyclobutyl, cyclopropyl, etc. Preferably, the alicyclic group is cyclohexyl, cyclopentyl, adamantly, or the like. The “alkenyl which may optionally be substituted with an alicyclic group” includes, for example, vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-methylpropenyl, etc., preferably, 2-methylpropenyl, etc.

The “alkynyl which may optionally be substituted with an alicyclic group” shown by R^(3″) is, for example, an unsubstituted straight or branched alkynyl having 2 to 6 carbon atoms, or a straight or branched alkynyl having 2 to 6 carbon atoms, which is substituted with an alicyclic group having, e.g., 1 to 10 carbon atoms. Examples of the alicyclic group include cyclohexyl, cyclopentyl, adamantyl, cyclobutyl, cyclopropyl, and the like. Preferably, the alicyclic group is cyclohexyl, cyclopentyl, adamantly, etc. Examples of the “alkynyl which may optionally be substituted with an alicyclic group” include ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, 5-hexynyl, and the like, preferably, 1-propynyl, etc.

The “aliphatic group” shown by R^(3″) includes, for example, cyclohexyl, cyclopentyl, adamantyl, cyclobutyl, cyclopropyl, and the like, preferably, cyclohexyl, etc.

The “heterocyclic group” shown by R^(3″) is, for example, a group formed by a 5- to 7-membered ring containing 1 to 3 atoms selected from the group consisting of N, O and S as the atoms for forming the ring, in addition to carbons and bound through carbon, a group formed by condensing at least two such rings and bound through carbon, or a group formed by condensing such rings with a benzene ring and bound through carbon. Examples of the “heterocyclic group” are thiophen-2-yl, 2-furanyl, 4-pyridyl, etc. In some embodiments of the present invention, the “heterocyclic group” is a heterocyclic group containing sulfur, e.g., thiophen-2-yl.

In a preferred embodiment of the present invention, R^(3″) is phenyl, p-hydroxyphenyl, benzyl, α-hydroxybenzyl, phenylethyl, phenylvinyl, cyclohexyl, cyclohexylmethyl, cyclohexylethyl, methyl, ethyl, propyl, 2-methylpropyl, 2-methylpropenyl, adamantylmethyl, cyclopentylmethyl or thiophen-2-yl. In a more preferred embodiment of the present invention, R^(3″) is benzyl.

In a still preferred embodiment of the present invention, R^(3″) is hydrogen atom, bromine atom or any one selected from the groups shown below:

(wherein each of R^(6″), R^(7″) and R^(8″) independently represents hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl, and R^(6″) and R^(8″) may be combined together with the carbon atom bound to each of R^(6″) and R^(8″) to form a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl).

As used herein, the “substituted or unsubstituted alkyl having 1 to 6 carbon atoms” shown by R^(6″), R^(7″) and R^(8″) is, for example, an alkyl having 1 to 6 carbon atoms and carrying 1 to 5 substituents which are the same or different, or an unsubstituted alkyl. The substituent is, for example, at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), etc. Specifically, the “substituted or unsubstituted alkyl having 1 to 6 carbon atoms” is methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl, fluoromethyl, a perfluoroalkyl (e.g., trifluoromethyl, perfluorohexyl), etc.

The “substituted or unsubstituted aryl” shown by R^(6″), R^(7″) and R^(8″) or the “substituted or unsubstituted aryl” formed by combining R^(6″) and R^(8″) together with the carbon atom bound to each of R^(6″) and R^(8″) is, for example, an aryl having 1 to 5 substituents which are the same or different, or an unsubstituted aryl. Examples of the substituent include at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl, 1-pyrrolidinyl), etc. In some embodiments of the present invention, the substituent is hydroxy group, nitro or dimethylamino. Specific examples are phenyl, a naphthyl (1-naphthyl, 2-naphthyl), a hydroxyphenyl (2-hydroxyphenyl, 3-hydroxyphenyl, 4-hydroxyphenyl), an aminophenyl (e.g., 4-dimethylaminophenyl), a nitrophenyl (e.g., 4-nitrophenyl), a fluorophenyl (e.g., 4-fluorophenyl), a trifluoromethylphenyl (e.g., 4-trifluoromethylphenyl), etc.

The “substituted or unsubstituted heteroaryl” shown by R^(6″), R^(7″) and R^(8″) or the “substituted or unsubstituted heteroaryl” formed by combining R^(6″) and R^(8″) together with the carbon atom bound to each of R^(6″) and R^(8″) is, for example, a heteroaryl having 1 to 5 substituents which are the same or different, or an unsubstituted heteroaryl. Examples of the substituent include at least one selected from the group consisting of a halogen (fluorine, chlorine, bromine or iodine), hydroxy group, nitro, cyano, amino, an alkyl having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, t-pentyl, hexyl, isohexyl), an alkoxyl having 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, isopentoxy, neopentoxy, t-pentoxy, hexyloxy, isohexyloxy), a dialkylamino having 1 to 6 carbon atoms (e.g., dimethylamino, diethylamino, ethylmethylamino, diisopropylamino, 1-piperidinyl and 1-pyrrolidinyl, preferably, dimethylamino, diethylamino, ethylmethylamino, diisopropylamino), an aryl (e.g., phenyl, naphthyl, anthranyl), a heteroaryl (e.g., a thienyl (2-thienyl, 3-thienyl), a furyl (2-furyl, 3-furyl), a pyrrolyl (2-pyrrolyl, 3-pyrrolyl), a pyridyl (2-pyridyl, 3-pyridyl, 4-pyridyl), imidazoyl, pyrazoyl, oxazoyl, thiazoyl, isoxazoyl, pyrimidyl, pyrazyl, pyridazoyl), etc. Specifically, the “substituted or unsubstituted heteroaryl” is a thienyl (2-thienyl, 3-thienyl), a benzothienyl (e.g., benzo[b]thiophen-2-yl, benzo[b]thiophen-3-yl), a thienothienyl (e.g., thieno[2,3-b]thienyl, thieno[3,2-b]thienyl, thieno[3,2-b:2,3-d]thienyl), a bithiophenyl (e.g., 2,2-bithiophen-5-yl), benzofuranyl, indoyl, indazoyl, benzimidazoyl, benzoxazoyl, benzisoxazoyl, quinolinyl, isoquinolinyl, quinoxalinyl, quinazolinyl, acridinyl, etc.

In some other embodiments of the present invention, coelenteramide analogue modified at the C-2-position includes the following compounds.

wherein R^(2″′) is a group selected from the groups shown below:

and R^(3″′) is hydrogen atom, bromine atom, a substituted or unsubstituted aryl, a substituted or unsubstituted arylalkyl, a substituted or unsubstituted arylalkenyl, a substituted or unsubstituted arylalkynyl, an alkyl which may optionally be substituted with an alicyclic group, an alkenyl which may optionally be substituted with an alicyclic group, an alkynyl which may optionally be substituted with an alicyclic group, an alicyclic group, or a heterocyclic group.

As used herein, the “substituted or unsubstituted aryl,” “substituted or unsubstituted arylalkyl,” “substituted or unsubstituted arylalkenyl,” “substituted or unsubstituted arylalkynyl,” “alkyl which may optionally be substituted with an alicyclic group,” “an alkenyl which may optionally be substituted with an alicyclic group,” “alkynyl which may optionally be substituted with an alicyclic group,” “alicyclic group” and “heterocyclic group” shown by R^(3″′) are the same as those defined for R^(3″).

In a preferred embodiment of the present invention, coelenteramide analogue includes the following compounds.

The fluorescent protein containing coelenteramide analogue in some embodiments of the present invention has the maximum fluorescence wavelength of 485 nm or more, for example, 485 nm or more, 486 nm or more, 487 nm or more, 488 nm or more, 489 nm or more, 490 nm or more, 491 nm or more, 492 nm or more, 493 nm or more, 494 nm or more, 495 nm or more, 496 nm or more, 497 nm or more, 498 nm or more, 499 nm or more, 500 nm or more, 510 nm or more, 515 nm or more, 520 nm or more, 525 nm or more, 530 nm or more, 535 nm or more, 540 nm or more, and 545 nm or more. More specifically, in coelenteramide analogues (4a to 4z) described above, coelenteramide analogue which can shift the maximum fluorescence wavelength to 485 nm or more includes 4a to 4l, 4n to 4p and 4u to 4z, preferably, 4a to 4d, 4f to 4l, 4p, 4n, 4v and 4x to 4z, more preferably, 4a, 4b, 4d, 4f to 4i, 4k, 4l and 4p, much more preferably, 4b, 4f, 4h, 4k and 4p, and most preferably, 4b, 4h and 4p.

The fluorescent protein containing coelenteramide analogue in some embodiments of the present invention shows a stronger fluorescence intensity than that of the corresponding coelenteramide analogue alone, for example, stronger by 1.5 times or more, 1.6 times or more, 1.7 times or more, 1.8 times or more, 1.9 times or more, 2.0 times or more, 2.1 times or more, 2.2 times or more, 2.3 times or more, 2.4 times or more, 2.5 times or more, 3.0 times or more, 4.0 times or more, 5.0 times or more, 10 times or more, 15 times or more, 20 times or more, 30 times or more, 40 times or more, 50 times or more, 60 times or more, 70 times or more, 80 times or more, 90 times or more, 100 times or more, 110 times or more, 120 times or more and 130 times or more. More specifically, among coelenteramide analogues (4a to 4z) described above, coelenteramide analogue in the form of fluorescent protein which can provide a stronger fluorescence intensity than that of the corresponding coelenteramide analogue alone includes 4a to 4p and 4r to 4z, preferably, 4a to 4g, 4l to 4p and 4r to 4z, more preferably, 4a, 4f, 4g and 4w, and most preferably, 4a, 4f and 4w.

The fluorescent protein containing coelenteramide analogue in some embodiments of the present invention provides different fluorescence spectra from those of the corresponding coelenteramide analogue alone. The maximum fluorescence wavelengths in the two cases are different by ±5 nm or more, ±10 nm or more, ±15 nm or more, ±20 nm or more, ±25 nm or more, ±30 nm or more, ±35 nm or more, ±40 nm or more, ±45 nm or more, ±50 nm or more, ±55 nm or more, ±60 nm or more, ±65 nm or more, ±70 nm or more, ±75 nm or more, ±80 nm or more, ±85 nm or more, ±90 nm or more, ±95 nm or more, or ±100 nm or more. More specifically, coelenteramide analogue which can change the maximum fluorescence intensity between the fluorescent protein and the corresponding coelenteramide alone includes 4a to 4n, 4p, 4r, 4s and 4u to 4z, preferably, 4a to 4e, 4f, 4h, 4l, 4k, 4m, 4n, 4p, 4u and 4w to 4z, among scoelenteramide analogues (4a to 4z) described above.

4. Method for Producing Coelenteramide Analogue of the Present Invention

4.1. Coelenteramide Analogue Modified at the C-3 Position

In coelenteramide analogue of the present invention, coelenteramide analogue modified at the C-3 position represented by general formula (II) below:

(wherein R^(3′) is the same as defined above) can be produced as follows.

That is, coelenteramide analogue represented by general formula (II) can be produced by reacting a compound represented by general formula (II-1) shown below:

(wherein R^(3′) is the same as defined above and Y^(1′) is hydrogen atom or a protecting group) with a compound represented by general formula (II-2) shown below:

(wherein X is a splitting-off group and Y^(2′) is hydrogen atom or a protecting group) to give a compound represented by general formula (II-3) shown below:

(wherein R^(3′), Y^(1′) and Y^(2′) are the same as defined above), or the like.

As used herein, the protecting groups shown by Y^(1′) and Y^(2′) independently represent, e.g., tert-butyldimethylsilyl (TBDMS), tert-butyldiphenylsilyl (TBDPS), trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), methoxymethyl (MOM), 2-methoxethoxyymethyl (MEM), 2-tetrahydropyranyl (THP), methyl (Me), tert-butyl (t-Bu), benzyl (Bn), p-methoxybenzyl (PMB), acetyl (Ac) or benzoyl (Bz); particularly preferred is TBDMS, Me, Bn or Ac.

The splitting-off group shown by X includes, for example, a halogen (e.g., chlorine, fluorine, bromine or iodine), a reactive residue of a sulfonic acid (e.g., methanesulfonyloxy, benzenesulfonyloxy or toluenesulfonyloxy), and an acyloxy for forming an acid anhydride (e.g., (4-Y^(2′)O)C₆H₄CH₂COO— (wherein Y^(2′) is the same as defined above)). Among them, a halogen is preferred and chlorine is more preferred.

The compound represented by general formula (II-1) can be produced by known production methods, for example, the methods described in Kishi et al. (1972) Tetrahedron Lett. 13, 2747-2748, Adamczyk et al. (2001) Org. Prep. Proced. Int. 33, 477-485 or Wael, F. D. et al. (2009) Bioorg. Med. Chem. 17, 4336-4344, or modifications of these methods.

The compound represented by general formula (II-2) can be produced by known production methods. Specifically, any compound can be produced either by reacting the corresponding carboxylic acid with an excess of thionyl chloride while heating to reflux followed by concentration under reduced pressure, or by reacting the corresponding carboxylic acid with oxalyl dichloride in a dichloromethane solvent in the presence of a catalytic amount of N,N-dimethylformamide (DMF) followed by concentration under reduced pressure. Alternatively, the compound may also be commercially available.

The compound represented by general formula (II-3) can be produced by known production methods. Specifically, any compound can be produced by reacting the compound represented by general formula (II-1) with the compound represented by general formula (II-2), e.g., in an organic solvent in the presence of a base or in a basic organic solvent.

In the compound represented by general formula (II-3) thus produced wherein Y^(1′) and Y^(2′) represent protecting groups, coelenteramide analogue represented by general formula (II) can be produced by removing the protecting groups from the compound represented by general formula (II-3). More specifically, coelenteramide analogue represented by general formula (II) can be produced by the method described in EXAMPLES below or modifications thereof.

Herein, where the protecting groups (Y^(1′) and Y^(2′)) are, e.g., TBDMS, the reagents used in the method for producing coelenteramide analogue represented by general formula (II) are fluorine reagents such as tetrabutylammonium fluoride (TBAF), potassium fluoride, hydrofluoric acid, etc. or acids such as acetic acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, perchloric acid, sulfuric acid, phosphoric acid, nitric acid, etc. These reagents may be used alone or as a mixture thereof. TBAF is particularly preferred.

Where the protecting groups (Y^(1′) and Y^(2′)) are, e.g., TBDMS, various solvents can be used as the solvent in the method for producing coelenteramide analogue represented by general formula (II), and examples include tetrahydrofuran (THF), dioxane, ether, acetonitrile, ethyl acetate, acetone, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), toluene, dichloromethane, methanol, ethanol, butanol, water, etc. These solvents can be used alone or as a mixture thereof.

In the method for producing coelenteramide analogue represented by general formula (II) where the protecting groups (Y^(1′) and Y^(2′)) are, e.g., TBDMS, the reaction temperature and reaction time are not particularly limited but are generally at −20° C. to 200° C. for 10 minutes to 24 hours, preferably at 0° C. to 100° C. for 10 minutes to 6 hours, more preferably, at room temperature to 50° C. for 30 minutes to 2 hours.

Further when the protecting groups (Y^(1′) and Y^(2′)) are, e.g., Me, various reagents can be used as the reagents in the method for producing coelenteramide analogue represented by general formula (II) in accordance with the method described in Inouye & Hosoya (2009) Biochem. Biophys. Res. Commun. 386, 617-622 or modifications thereof. For example, boron tribromide or pyridinium chloride can be used, and boron tribromide is particularly preferred.

In the method for producing coelenteramide analogue represented by general formula (II), solvents can be used. When the protecting groups (Y^(1′) and Y^(2′)) are, e.g., Me, various solvents can be used and examples are dichloromethane, chloroform, tetrahydrofuran (THF), dioxane, ether, acetonitrile, ethyl acetate, acetone, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), toluene, etc. These solvents can be used alone or as a mixture thereof.

In the method for producing coelenteramide analogues represented by general formula (II), where the protecting groups (Y^(1′) and Y^(2′)) are, e.g., Me, the reaction temperature and reaction time are not particularly limited but are generally at −78° C. to 200° C. for 10 minutes to 72 hours, preferably, 0° C. to 150° C. for 30 minutes to 36 hours, and more preferably, at room temperature to 60° C. for an hour to 12 hours.

4.2. Coelenteramide Analogue Modified at the C-2 Position

4.2.1. Coelenteramide Analogue Represented by General Formula (III)

In coelenteramide analogues of the present invention, coelenteramide analogue modified at the C-2 position, which is represented by general formula (III) shown below:

(wherein Z¹ and R^(3″) are the same as defined above) can be produced as follows.

The above compound can be produced by first reacting a compound represented by general formula (III-1) shown below:

(wherein R^(3″) is the same as defined above and Y^(1″) is hydrogen atom or a protecting group) with a compound represented by general formula (III-2) shown below:

(wherein Z¹ is the same as defined above and Y^(2″) is hydrogen atom or a protecting group) to give a compound represented by general formula (III-3) shown below:

(wherein R^(3″), Y^(1″), Y^(2″) and Z¹ are the same as defined above), and so on.

As used herein, the “protecting groups” shown by Y^(1″) and Y^(2″) are the same as those described for Y^(1′) and Y^(2′).

The compound represented by general formula (III-1) can be produced by known production methods, for example, the methods described in Y. Kishi et al., Tetrahedron Lett., 13, 2747-2748 (1972), M. Adamczyk et al., Org. Prep. Proced. Int., 33, 477-485 (2001), or F. D. Wael et al., Bioorg. Med. Chem., 17, 4336-4344 (2009), or modifications of these methods.

The compound represented by general formula (III-2) can be produced by known production methods, for example, the method described in S. Knaggs et al., Org. Biomol. Chem., 3, 4002-4010 (2005) or modifications thereof. Alternatively, the compound is commercially available.

The compound represented by general formula (III-3) can be produced by known production methods. Specifically, any compound can be produced by reacting the compound represented by general formula (III-1) with the compound represented by general formula (III-2), e.g., in an organic solvent in the presence of a base or in a basic organic solvent.

In the compound represented by general formula (III-3) thus produced wherein Y^(1″) and Y^(2″) represent protecting groups, coelenteramide analogues represented by general formula (III) can be produced by removing the protecting groups from the compound represented by general formula (III-3). More specifically, coelenteramide analogues represented by general formula (III) can be produced by the method described in EXAMPLES below or modifications thereof.

Herein, where the protecting groups (Y^(1″) and Y^(2″)) are, e.g., TBDMS, the reagents used in the method for producing coelenteramide analogues represented by general formula (III) are fluorine reagents such as tetrabutylammonium fluoride (TBAF), potassium fluoride, hydrofluoric acid, etc. or acids such as acetic acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, perchloric acid, sulfuric acid, phosphoric acid, nitric acid, etc. These reagents may be used alone or as a mixture thereof. TBAF is particularly preferred.

Where the protecting groups (Y^(1″) and Y^(2″)) are, e.g., TBDMS, various solvents can be used as the solvent in the method for producing coelenteramide analogues represented by general formula (II), and examples include tetrahydrofuran (THF), dioxane, ether, acetonitrile, ethyl acetate, acetone, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), toluene, dichloromethane, methanol, ethanol, butanol, water, etc. These solvents can be used alone or as a mixture thereof.

In the method for producing coelenteramide analogues represented by general formula (III), when the protecting groups (Y^(1″) and Y^(2″)) are, e.g., TBDMS, the reaction temperature and reaction time are not particularly limited but are generally at −20° C. to 200° C. for 10 minutes to 24 hours, preferably, at 0° C. to 100° C. for 10 minutes to 6 hours, and more preferably, at room temperature to 50° C. for 30 minutes to 2 hours.

Also, when the protecting groups (Y^(1″) and Y^(2″)) are, e.g., Me, various reagents can be used as the reagents in the method for producing coelenteramide analogues represented by general formula (III) in accordance with the method described in Inouye & Hosoya, Biochem. Biophys. Res. Commun., 386, 617-622 (2009), or modifications thereof. For example, boron tribromide or pyridinium chloride can be used, and boron tribromide is particularly preferred.

In the method for producing coelenteramide analogues represented by general formula (III), solvents can be used and where the protecting groups (Y^(1″) and Y^(2″)) are, e.g., Me, various solvents can be used. Examples are dichloromethane, chloroform, tetrahydrofuran (THF), dioxane, ether, acetonitrile, ethyl acetate, acetone, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), toluene, etc. These solvents can be used alone or as a mixture thereof.

In the method for producing coelenteramide analogues represented by general formula (III) where the protecting groups (Y^(1″) and Y^(2″)) are, e.g., Me, the reaction temperature and reaction time are not particularly limited but are generally at −78° C. to 200° C. for 10 minutes to 72 hours, preferably, at 0° C. to 150° C. for 30 minutes to 36 hours, and more preferably, at room temperature to 60° C. for an hour to 12 hours.

4.2.2. Coelenteramide Analogue Represented by General Formula (IV)

In coelenteramide analogues of the present invention, coelenteramide analogue represented by general formula (IV) shown below, which is modified at the C-2 position can be prepared as follows:

(wherein R^(2″′) and R^(3″′) are the same as defined above).

That is, a compound represented by general formula (IV-1) shown below:

(wherein R^(3″′) is the same as defined above and Y^(1″′) is hydrogen atom or a protecting group) is reacted with a compound represented by general formula (IV-2) shown below:

(wherein X is a splitting-off group and R^(2″′) is a group selected from:

(wherein Y^(1″′) is hydrogen atom or a protecting group) to give a compound represented by general formula (IV-3-1) or (IV-3-2) shown below:

(wherein R^(2″′), R^(3″′) and Y^(1″′) are the same as defined above), and so on.

Herein, the splitting off group shown by X includes, for example, a halogen (e.g., chlorine, fluorine, bromine or iodine), a reactive residue of a sulfonic acid (e.g., methanesulfonyloxy, benzenesulfonyloxy or toluenesulfonyloxy), and an acyloxy for forming an acid anhydride (e.g., (4-Y^(1″′)O)C₆H₄CH₂COO— (wherein Y^(1″′) is the same as defined above)). Among them, a halogen is preferred and chlorine is more preferred.

The compound represented by general formula (IV-1) can be produced by known production methods, for example, the methods described in Kishi et al., Tetrahedron Lett., 13, 2747-2748 (1972), Adamczyk et al., Org. Prep. Proced. Int., 33, 477-485 (2001), or modifications of these methods.

The compound represented by general formula (IV-2) can be produced by known production methods. Specifically, any compound can be produced either by reacting the corresponding carboxylic acid with an excess of thionyl chloride while heating to reflux followed by concentration under reduced pressure, or by reacting the corresponding carboxylic acid with oxalyl dichloride in a dichloromethane solvent in the presence of a catalytic amount of N,N-dimethylformamide (DMF) followed by concentration under reduced pressure. Alternatively, the compound may also be commercially available.

The compound represented by general formula (IV-3-1) or general formula (IV-3-2) can be produced by known production methods. Specifically, any compound can be produced by reacting the compound represented by general formula (IV-1) with the compound represented by general formula (IV-2), e.g., in an organic solvent in the presence of a base or in a basic organic solvent.

In the compound represented by general formula (IV-3-1) or general formula (IV-3-2) thus produced wherein Y^(1″′) and Y^(2″′) represent protecting groups, coelenteramide analogues represented by general formula (IV) can be produced by removing the protecting groups from the compound represented by general formula (IV-3-1) or general formula (IV-3-2). More specifically, coelenteramide analogues represented by general formula (IV) can be produced by the method described in EXAMPLES below or modifications thereof.

Herein, where the protecting groups (Y^(1″′) and Y^(2″″)) are, e.g., TBDMS, the reagents used in the method for producing coelenteramide analogues represented by general formula (IV) are fluorine reagents such as tetrabutylammonium fluoride (TBAF), potassium fluoride, hydrofluoric acid, etc. or acids such as acetic acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, perchloric acid, sulfuric acid, phosphoric acid, nitric acid, etc. These reagents may be used alone or as a mixture thereof. TBAF is particularly preferred.

Where the protecting groups (Y^(1″′) and Y^(2″′)) are, e.g., TBDMS, various solvents can be used as the solvent in the method for producing coelenteramide analogues represented by general formula (IV), and examples include tetrahydrofuran (THF), dioxane, ether, acetonitrile, ethyl acetate, acetone, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), toluene, dichloromethane, methanol, ethanol, butanol, water, etc. These solvents can be used alone or as a mixture thereof.

In the method for producing coelenteramide analogue represented by general formula (IV) wherein the protecting groups (Y^(1″′) and Y^(2″′)) are, e.g., TBDMS, the reaction temperature and reaction time are not particularly limited but are generally at −20° C. to 200° C. for 10 minutes to 24 hours, preferably, at 0° C. to 100° C. for 10 minutes to 6 hours, and more preferably, at room temperature to 50° C. for 30 minutes to 2 hours.

Further when the protecting groups (Y^(1″′) and Y^(2″′)) are, e.g., Me, various reagents can be used as the reagent in the method for producing coelenteramide analogue represented by general formula (IV) in accordance with the method described in Inouye & Hosoya (2009) Biochem. Biophys. Res. Commun. 386, 617-622 or modifications thereof. For example, boron tribromide or pyridinium chloride can be used, and boron tribromide is particularly preferred.

In the method for producing coelenteramide analogue represented by general formula (IV), solvents can be used. When the protecting groups (Y^(1″′) and Y^(2″″)) are, e.g., Me, various solvents can be used and examples are dichloromethane, chloroform, tetrahydrofuran (THF), dioxane, ether, acetonitrile, ethyl acetate, acetone, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), toluene, etc. These solvents can be used alone or as a mixture thereof.

In the method for producing coelenteramide analogue represented by general formula (IV) where the protecting groups (Y^(1″′) and Y^(2″′)) are, e.g., Me, the reaction temperature and reaction time are not particularly limited but are generally at −78° C. to 200° C. for 10 minutes to 72 hours, preferably, at 0° C. to 150° C. for 30 minutes to 36 hours, and more preferably, at room temperature to 60° C. for an hour to 12 hours.

5. Method for Producing the Calcium-Binding Photoprotein

5.1. Production from Coelenterazine Analogue

The calcium-binding photoprotein of the present invention can be produced or regenerated by contacting coelenterazine analogue of the present invention described above with an apoprotein of the calcium-binding photoprotein thereby to obtain the calcium-binding photoprotein.

As used herein, the term “contact” means that coelenterazine analogue of the present invention and an apoprotein of the calcium-binding photoprotein are allowed to be present in the same reaction system, and includes, for example, states that an apoprotein of the calcium-binding photoprotein is added to a container charged with coelenterazine analogue of the present invention, coelenterazine analogue of the present invention is added to a container charged with an apoprotein of the calcium-binding photoprotein, coelenterazine analogue of the present invention is mixed with an apoprotein of the calcium-binding photoprotein, and the like.

In some embodiments of the present invention, the contact is effected at a low temperature in the presence of a reducing agent (e.g., mercaptoethanol, dithiothreitol, etc.) and oxygen. More specifically, the calcium-binding photoprotein of the present invention can be produced or regenerated by the methods described in, e.g., Shimomura, O. et al. Biochem. J. 251, 405-410 (1988), Shimomura, O. et al. Biochem. J. 261, 913-920 (1989), etc. The calcium-binding photoprotein of the present invention exists as a complex which, in the presence of oxygen, generates from a peroxide of coelenterazine analogue produced from coelenterazine analogue of the invention and molecular oxygen, and an apoprotein. When calcium ions bind to the complex described above, the complex emits a transient light to generate coelenteramide analogue as the oxide of coelenterazine analogue and carbon dioxide. The complex described above is sometimes referred to as the “photoprotein of the present invention.”

Examples of the apoprotein used to produce the photoprotein of the present invention include apoaequorin, apoclytin-I, apoclytin-II, apobelin, apomitrocomin, apomineopsin, apobervoin, and the like. In some embodiments of the present invention, the apoprotein is apoaequorin, apobelin, apoclytin-I, apoclytin-II, mitrocomin, etc., e.g., apoaequorin. These apoproteins may be obtained from natural sources or genetically engineered. Furthermore, the amino acid sequence may also be mutated from the native sequence by gene recombination technology, as long as the apoproteins are capable of producing the calcium-binding photoprotein.

The nucleotide sequences and amino acid sequences of the apoproteins of photoproteins obtained from the nature (native apoproteins) are as follows. The nucleotide sequence and amino acid sequence of native apoaequorin are shown by SEQ ID NO: 1 and SEQ ID NO: 2, respectively. The nucleotide sequence and amino acid sequence of native apoclytin-I are shown by SEQ ID NO: 3 and SEQ ID NO: 4, respectively. The nucleotide sequence and amino acid sequence of native apoclytin-II are shown by SEQ ID NO: 5 and SEQ ID NO: 6, respectively. The nucleotide sequence and amino acid sequence of native apomitrocomin are shown by SEQ ID NO: 7 and SEQ ID NO: 8, respectively. The nucleotide sequence and amino acid sequence of native apobelin are shown by SEQ ID NO: 9 and SEQ ID NO: 10, respectively. The nucleotide sequence and amino acid sequence of native apobervoin are shown by SEQ ID NO: 11 and SEQ ID NO: 12, respectively.

The apoprotein mutated by recombinant technology is a protein selected from the group consisting of (a) to (c) below:

(a) a protein comprising the amino acid sequence of native apoprotein in which 1 or more amino acids are deleted, substituted, inserted and/or added, and having the activity or function of the apoprotein of the calcium-binding photoprotein;

(b) a protein comprising an amino acid sequence which has 90% or more homology to the amino acid sequence of native apoprotein, and having the activity or function of the apoprotein of the calcium-binding photoprotein; and,

(c) a protein comprising an amino acid sequence encoded by a polynucleotide that hybridizes under stringent conditions to a polynucleotide comprising a nucleotide sequence complementary to the nucleotide sequence of native apoprotein, and having the activity or function of the apoprotein of the calcium-binding photoprotein.

Examples of the “native apoprotein” described above are apoaequorin, apoclytin-I, apoclytin-II, apobelin, apomitrocomin, apomineopsin, apobervoin, etc. In an embodiment of the present invention, the apoprotein is apoaequorin, apoclytin-I, apoclytin-II, apobelin, apomitrocomin, etc., preferably apoaequorin. The amino acid sequences and nucleotide sequences of these native apoproteins are the same as described above.

The “activity or function of the apoprotein of the calcium-binding photoprotein” means the activity or function of the apoprotein which binds to a peroxide of coelenterazine or a peroxide of coelenterazine analogue to produce the calcium-binding photoprotein. Specifically, “the protein binds to a peroxide of coelenterazine or a peroxide of coelenterazine analogue to produce the calcium-binding photoprotein” means not only (1) that the apoprotein binds to the peroxide of coelenterazine or the peroxide of coelenterazine analogue to produce the photoprotein, but also (2) that the apoprotein is brought in contact with coelenterazine or its analogues in the presence of oxygen to produce the photoprotein (complex) containing the apoprotein and the peroxide of coelenterazine or the peroxide of coelenterazine analogue. As used herein, the term “contact” means that the apoprotein and coelenterazine or its analogue are allowed to be present in the same reaction system, and includes, for example, addition of the apoprotein to a container charged with coelenterazine or its analogue, addition of coelenterazine or its analogue to a container charged with the apoprotein, mixing of the apoprotein with coelenterazine or its analogue, and the like. “Coelenterazine analogue” refers to a compound capable of constituting as the apoprotein the calcium-binding photoprotein such as aequorin, etc. as in coelenterazine. Examples of coelenterazine or its analogue are, in addition to coelenterazine analogue of the present invention, coelenterazine, h-coelenterazine, f-coelenterazine, cl-coelenterazine, n-coelenterazine, cp-coelenterazine, ch-coelenterazine, hch-coelenterazine, fch-coelenterazine, e-coelenterazine, ef-coelenterazine, ech-coelenterazine, hcp-coelenterazine, and the like. These coelenterazine and analogues of the present invention can be produced, e.g., by the method described in EXAMPLES below or its modifications. The other coelenterazine and analogues thereof can be produced by the methods described in, e.g., Shimomura et al. (1988) Biochem. J. 251, 405-410, Shimomura et al. (1989) Biochem. J. 261, 913-920 and Shimomura et al. (1990) Biochem. J. 270, 309-312, or modifications thereof. Alternatively, these compounds are commercially available from Chisso Corp., Wako Pure Chemicals, Promega Inc., etc. and such commercial products may also be used.

The range of “1 or more” in “the amino acid sequence in which 1 or more amino acids are deleted, substituted, inserted and/or added” is, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 9, 1 to 8, 1 to 7, 1 to 6 (1 to several), 1 to 5, 1 to 4, 1 to 3, 1 to 2, and 1. In general, the less the number of amino acids deleted, substituted, inserted or added, the more preferable. In the deletion, substitution, insertion and addition of the amino acid residues described above, two or more may occur concurrently. Such regions can be acquired by using site-directed mutagenesis described in Sambrook J. et al., Molecular Cloning: A Laboratory Manual, Third Edition, Cold Spring Harbor Laboratory Press (2001); Ausbel F. M. et al., Current Protocols in Molecular Biology, Supplement 1-38, John Wiley and Sons (1987-1997); Nuc. Acids. Res., 10, 6487 (1982); Proc. Natl. Acad. Sci. USA, 79, 6409 (1982); Gene, 34, 315 (1985); Nuc. Acids. Res., 13, 4431 (1985); Proc. Natl. Acad. Sci. USA, 82, 488 (1985); etc.

The range of “90% or more” in the “amino acid sequence which has 90% or more homology” is, for example, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, 99.8% or more, or 99.9% or more. It is generally preferable for the numerical value indicating the degree of homology to be higher. The homology between amino acid sequences or nucleotide sequences can be determined using a sequencing program such as BLAST (see, e.g., Altzchul, S. F. et al., J. Mol. Biol., 215, 403 (1990), etc.) or the like. When BLAST is used, the default parameters for the respective programs are used.

The “polynucleotide that hybridizes under stringent conditions” described above refers to a polynucleotide (e.g., DNA) which is obtained by, for example, colony hybridization, plaque hybridization, Southern hybridization, etc., using as a probe all or part of a polynucleotide comprising a nucleotide sequence complementary to the nucleotide sequence of native apoprotein or a polynucleotide encoding the amino acid sequence of native apoprotein. Specific examples include a polynucleotide which can be identified by performing hybridization at 65° C. in the presence of 0.7 to 1.0 mol/L NaCl using a filter on which the polynucleotide from a colony or plaque is immobilized, then washing the filter at 65° C. with an SSC (saline-sodium citrate) solution having a concentration of 0.1 to 2 times (a 1×SSC solution is composed of 150 mmol/L of sodium chloride and 15 mmol/L of sodium citrate).

Hybridization may be performed in accordance with modifications of the methods described in textbooks of experiment, e.g., Sambrook, J. et al.: Molecular Cloning: A Laboratory Manual, Third Edition, Cold Spring Harbor Laboratory Press (2001), Ausbel F. M. et al., Current Protocols in Molecular Biology, Supplement 1-38, John Wiley and Sons (1987-1997), Glover D. M. and Hames B. D., DNA Cloning 1: Core Techniques, A practical Approach, Second Edition, Oxford University Press (1995), etc., or their modifications.

As used herein, “stringent conditions” may refer to less stringent conditions, moderately stringent conditions and highly stringent conditions. The “less stringent conditions” are, for example, the conditions under 5×SSC, 5×Denhardt's solution, 0.5% (w/v) SDS and 50% (v/v) formamide at 32° C. The “moderately stringent conditions” are, for example, the conditions under 5×SSC, 5×Denhardt's solution, 0.5% (w/v) SDS and 50% (v/v) formamide at 42° C. The “highly stringent conditions” are, for example, the conditions under 5×SSC, 5×Denhardt's solution, 0.5% (w/v) SDS and 50% (v/v) formamide at 50° C. The more stringent the conditions are, the higher the complementarity required for double strand formation. Specifically, for example, under these conditions, a polynucleotide (e.g., DNA) of higher homology is expected to be obtained efficiently at higher temperatures, although multiple factors are involved in hybridization stringency, including temperature, probe concentration, probe length, ionic strength, time and base concentration; one skilled in the art may appropriately select these factors to realize a similar stringency.

When a commercially available kit is used for the hybridization, for example, AlkPhos Direct Labeling Reagents (manufactured by Amersham Pharmacia) can be used. According to the protocol bound to the kit in this case, incubation with a labeled probe is performed overnight, the membrane is then washed with a primary wash buffer containing 0.1% (w/v) SDS at 55° C., and finally the hybridized DNA can be detected.

Other hybridizable polynucleotides include, as calculated by a sequencing program such as BLAST or the like using the default parameters, DNAs having homology of 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 88% or more, 90% or more, 92% or more, 95% or more, 97% or more, 98% or more, 99% or more, 99.3% or more, 99.5% or more, 99.7% or more, 99.8% or more, or 99.9% or more, to the polynucleotide encoding the amino acid sequence of the apoprotein. The homology of an amino acid sequence or a nucleotide sequence can be determined using the method described hereinabove.

Examples of the recombinant apoprotein which can be used in the present invention include recombinant aequorin described in Shimomura, O. and Inouye, S. Protein Express. Purif (1999) 16: 91-95, recombinant clytin-I described in Inouye, S, and Sahara, Y. Protein Express. Purif (2007) 53: 384-389, recombinant clytin-II described in Inouye, S. J. Biochem. (2008) 143: 711-717, and the like.

The calcium-binding photoprotein thus produced may be further purified. Purification of the calcium-binding photoprotein can be performed in a conventional manner of separation/purification. The separation/purification includes, for example, precipitation with ammonium sulfate, gel filtration chromatography, ion exchange chromatography, affinity chromatography, reversed phase high performance liquid chromatography, dialysis, ultrafiltration, etc., alone or in an appropriate combination of these techniques.

The photoprotein in some embodiments of the present invention exhibits different luminescence properties from those of known photoproteins. The photoprotein in a preferred embodiment of the present invention provides a longer half decay time of luminescence, which is a time period in which the luminescence becomes half of the maximum luminescence intensity, when compared to a photoprotein containing coelenterazine as a light emitting substrate. Furthermore, the photoprotein in a more preferred embodiment of the present invention provides different luminescence spectra from luminescence spectra of the corresponding fluorescent protein prepared by causing luminescence of the photoprotein in the presence of calcium.

5.2. Production from Green Fluorescent Protein (gFP)-Like Protein

As illustrated in FIG. 8, the calcium-binding photoprotein such as aequorin, etc. can be produced by contacting coelenterazine or its analogues with the gFP-like protein of the present invention in the presence of a chelating agent such as EDTA, etc., for sequestering calcium ions or divalent or trivalent ions replaceable for the calcium ions thereby to obtain the calcium-binding photoprotein. The term “contact” means that the gFP-like protein of the present invention and coelenterazine or its analogue are allowed to be present in the same reaction system, and includes, for example, addition of the gFP-like protein of the present invention to a container charged with coelenterazine or its analogue, addition of coelenterazine or its analogue of the present invention to a container charged with the gFP-like protein of the present invention, mixing of the gFP-like protein of the present invention with coelenterazine or its analogue, and the like.

The gFP-like protein of the present invention used to produce the calcium-binding photoprotein of the present invention is described hereinbelow.

Examples of coelenterazine or its analogue used to produce the calcium-binding photoprotein of the present invention include, in addition to coelenterazine analogue of the present invention, coelenterazine, h-coelenterazine, f-coelenterazine, cl-coelenterazine, n-coelenterazine, cp-coelenterazine, ch-coelenterazine, hch-coelenterazine, fch-coelenterazine, e-coelenterazine, ef-coelenterazine, ech-coelenterazine, hcp-coelenterazine, and the like, preferably coelenterazine, h-coelenterazine and e-coelenterazine. These coelenterazine and analogues thereof are available as described above.

The amount of coelenterazine or its analogue used to produce the calcium-binding photoprotein is not particularly limited, and is, e.g., 1.2 mol or more per mol of the gFP-like protein.

In the method for producing the calcium-binding photoprotein, the reaction temperature and reaction time are not particularly limited and are, for example, at 0° C. to 42° C. for 0.1 to 2 hours, at 4° C. to 37° C. for 0.1 to 2 hours, or at 4° C. to 15° C. for 0.1 to 24 hours.

It is preferred to carry out the reaction of the gFP-like protein of the present invention with coelenterazine or its analogue in the presence of the chelating agent for sequestering calcium ions or divalent or trivalent ions replaceable for the calcium ions. The chelating agent used to produce the gFP-like protein in the present invention is the same as described above, and may be any agent but is not particularly limited, so long as it strongly binds to calcium ions or divalent or trivalent ions replaceable for the calcium ions. Examples of the chelating agent include ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA), N-(2-hydroxyethyl)iminodiacetic acid (HIDA) and the like. As used herein, the calcium ions or divalent or trivalent ions replaceable for the calcium ions are the same as those described above.

The amount of the chelating agent used to produce the gFP-like protein is not particularly limited unless its concentration affects regeneration of the gFP-like protein. Since it is demonstrated that 3 mols of calcium ions bind to 1 mol of ion apoaequorin, e.g., 3 mols or more are preferred.

In a more preferred embodiment of the present invention, the fluorescent protein is reacted with coelenterazine or its analogue in the presence of a reducing agent. Examples of the reducing agent used herein include dithiothreitol (DTT), mercaptoethanol, etc. The amount of the reducing agent used to produce the calcium-binding photoprotein is not particularly limited, so long as the amount does not affect the regeneration, but the concentration is preferably sufficient to prevent the S—S bonds formed by the presence of cysteine residues at the three positions of apoaequorin. The concentration is, for example, 1 mM dithiothreitol or 0.1% (v/v) mercaptoethanol in a final concentration.

6. Use of the Photoprotein of the Invention

(1) Detection or Quantitative Determination of Calcium Ions

The photoprotein of the present invention obtained as described above is a non-covalent complex of an apoprotein and a peroxide of coelenterazine analogue formed from coelenterazine analogue and molecular oxygen and is a photoprotein (holoprotein) that emits light by the action of calcium ions. Therefore, the photoprotein of the invention can be used for the detection or quantitative determination of calcium ions.

The detection or quantitative determination of calcium ions can be performed, for example, by adding a sample solution directly to a solution of the photoprotein and measuring the luminescence generated. Alternatively, calcium ions can also be detected or quantified by adding a solution of the photoprotein to a sample solution and measuring the luminescence generated. Also, the photoprotein above may be formed by previously contacting an aqueous apoprotein solution with coelenterazine analogue of the present invention prior to its addition to the assay system for the detection or quantitative determination of calcium ions and the resulting photoprotein may be provided for use. The photoprotein comprising an apoprotein and a peroxide of coelenterazine analogue may also be formed in the assay system by contacting the apoprotein with coelenterazine analogue. The photoprotein formed is a complex (photoprotein) of the apoprotein and the peroxide of coelenterazine analogue of the invention. The complex (i.e., the photoprotein of the present invention) emits light dependently on the calcium ion concentration.

The detection or quantitative determination of calcium ions can be performed by measuring the luminescence of the photoprotein of the invention through the action of calcium ions, using a luminometer. Luminometers which may be used include commercially available instruments, such as a Centro LB 960 (manufactured by Berthold, Inc.), etc. The calcium ion concentration can be quantitatively determined by preparing a luminescence standard curve for known calcium ion concentrations using the photoprotein.

Coelenterazine analogue of the present invention may also be used for the detection of changes in the intracellular calcium ion concentration under the physiological conditions by preparing the photoprotein comprising an apoprotein and a peroxide of coelenterazine analogue and injecting the photoprotein directly into cells by means of microinjection, etc.

Coelenterazine analogue of the present invention may also be used to produce the photoprotein, which is performed, in addition to the injection using techniques such as microinjection, by intracellularly expressing a gene for the apoprotein (a polynucleotide encoding the apoprotein) to produce the protein in the cells and adding coelenterazine analogue of the present invention to the resulting apoprotein from the external cells.

Using the photoprotein of the present invention thus introduced into cells or produced in cells, changes in the intracellular calcium ion concentration caused by external stimulation (e.g., stimulation with receptor-associated drugs, etc.) can also be determined.

(2) Use as a Reporter Protein, Etc. Utilizing Luminescence

The photoprotein of the present invention can also be used as a reporter protein to determine the transcription activity of a promoter, etc. A polynucleotide encoding an apoprotein is fused to a target promoter or other expression control sequence (e.g., an enhancer, etc.) to construct a vector. The vector described above is transfected to a host cell, and coelenterazine analogue of the present invention is brought in contact with the host cell. By detecting the luminescence from the photoprotein of the present invention, the activity of the target promoter or other expression control sequence can be determined. As used herein, the term “contact” means that a host cell and coelenterazine analogue of the present invention are allowed to be present in the same culture/reaction system, and includes, for example, addition of coelenterazine analogue of the present invention to a culture container charged with a host cell, mixing of a host cell with coelenterazine analogue of the present invention, culture of a host cell in the presence of coelenterazine analogue of the present invention, and the like.

The present invention further provides a kit used for the measurement of transcription activity of a promoter, etc. In some embodiments of the present invention, the kit comprises coelenterazine analogue of the present invention, cells containing a polynucleotide (e.g., DNA) encoding the apoprotein of the calcium-binding photoprotein, etc. Reagent such as coelenterazine analogue of the present invention, etc. may be dissolved in a suitable solvent and prepared to be suitable for storage. The solvent which may be used is at least one selected from the group consisting of water, ethanol, various buffer solutions, and the like. The kit may additionally comprise, if necessary, at least one selected from the group consisting of a container designed therefor, other necessary accessories and an instruction manual, and the like.

(3) Use as a Detection Marker Utilizing Luminescence

The photoprotein of the present invention can be used as a marker for detection by luminescence. The detection marker of the present invention can be used to detect a target substance in, e.g., immunoassay, hybridization assay, etc. The photoprotein of the present invention can be used in the form bound to a target substance (protein, nucleic acid, etc.) in a conventional manner including chemical modification. Detection methods using the detection marker can be performed in a conventional manner. The detection marker of the present invention can also be used to determine the distribution of a target substance by expressing the marker, e.g., as a fusion protein of the apoprotein and the target substance, then inserting the fusion protein into cells by means of microinjection or the like and contacting them with coelenterazine analogue of the present invention thereby to produce the photoprotein of the present invention. As used herein, the term “contact” means that cells and coelenterazine analogue of the present invention are allowed to be present in the same culture/reaction system, and includes, for example, addition of coelenterazine analogue of the present invention to a culture container charged with cells, mixing of cells with coelenterazine analogue of the present invention, culture of host cells in the presence of coelenterazine analogue of the present invention, and the like.

The distribution of such a target protein, etc. can be determined by a method for detection such as luminescence imaging. The apoprotein can also be used after expression in cells, in addition to the insertion into cells by means of microinjection, etc.

The present invention further provides a kit used for the detection of a target substance in an immunoassay, hybridization assay, etc. The kit in some embodiments of the present invention comprises the photoprotein of the present invention. The kit in another embodiment of the present invention comprises coelenterazine analogue of the present invention, a cell containing a polynucleotide (e.g., DNA) encoding the apoprotein of the calcium-binding photoprotein, etc. Reagent such as coelenterazine analogue, etc. may be dissolved in a suitable solvent and prepared to be suitable for storage. The solvent which may be used is at least one selected from the group consisting of water, ethanol, various buffer solutions, and the like. The kit may additionally comprise, if necessary, at least one selected from the group consisting of a container designed therefor, other necessary accessories and an instruction manual, and the like.

(4) Material for Amusement Supplies

The complex (photoprotein of the present invention) comprising the apoprotein and a peroxide of coelenterazine analogue of the present invention emits light only by binding to a trace of calcium ions. The photoprotein of the present invention can be preferably used as a luminescence material for amusement supplies. Examples of such amusement supplies are luminescent soap bubbles, luminescent ice, luminescent candies, luminescent color paints, etc. The amusement supplies of the present invention can be prepared in a conventional manner.

(5) Bioluminescence Resonance Energy Transfer (BRET) Method

The photoprotein of the present invention can be used for analyses including an analysis of biological functions, an assay for enzyme activities, etc., based on the principle of intermolecular interaction by the bioluminescence resonance energy transfer (BRET) method.

For example, using the photoprotein of the invention as a donor protein and an organic compound or a fluorescent protein as an acceptor protein, the interaction between the proteins can be detected by generating bioluminescence resonance energy transfer (BRET) between them. In some embodiments of the present invention, the organic compound used as an acceptor protein is Hoechist 3342, Indo-1, DAP1, etc. In another embodiment of the present invention, the fluorescent protein used as an acceptor protein is a green fluorescent protein (GFP), a blue fluorescent protein (BFP), a mutant GFP fluorescent protein, phycobilin, etc. In a preferred embodiment of the present invention, the physiological functions to be analyzed include an orphan receptor (in particular, G-protein conjugated receptor), apoptosis, transcription regulation by gene expression, etc. Still in a preferred embodiment of the present invention, the enzyme to be analyzed is protease, esterase, kinase, etc.

Analysis of the physiological functions by the BRET method may be performed by known methods, for example, by modifications of the methods described in Biochem. J. 2005, 385, 625-637, Expert Opin. Ther. Targets, 2007 11: 541-556, etc. Assay for the enzyme activity may also be performed by known methods, for example, by modifications of the methods described in Nat. Methods 2006, 3:165-174, Biotechnol. J. 2008, 3: 311-324, etc.

The present invention further provides a kit used for the analysis method described above. The kit comprises the photoprotein of the present invention and the organic compound and/or the fluorescent protein. Reagent such as the photoprotein of the present invention, organic compounds, fluorescent proteins, etc. may be dissolved in a suitable solvent and prepared to be suitable for storage. The solvent which may be used is at least one selected from the group consisting of water, ethanol, various buffer solutions, and the like. The kit may additionally comprise, if necessary, at least one selected from the group consisting of a container designed therefor, other necessary accessories and an instruction manual, and the like.

7. Fluorescent Protein

As illustrated in FIG. 8, the blue fluorescent protein (BFP)-like fluorescent protein can be produced by contacting coelenteramide or its analogues with an apoprotein such as apoaequorin, etc. Alternatively, the BFP-like fluorescent protein can also be produced by generating luminescence through contact of the calcium-binding photoprotein such as aequorin, etc. with calcium ions or bivalent or trivalent ions replaceable for the calcium ions to obtain the BFP-like protein.

On the other hand, the green fluorescent protein (gFP)-like fluorescent protein can be produced by contacting coelenteramide or its analogues with an apoprotein such as apoaequorin, etc. in the presence of a chelating agent for sequestering calcium ions or divalent or trivalent ions replaceable for the calcium ions thereby to obtain the gFP-like fluorescent protein. Alternatively, the gFP-like fluorescent protein can also be produced by treating the BFP-like fluorescent protein with a chelating agent such as EDTA, etc., for sequestering calcium ions or divalent or trivalent ions replaceable for the calcium ions.

7.1. Blue Fluorescent Protein (BFP)-Like Fluorescent Protein

7.1.1. Production of Blue Fluorescent Protein (BFP)-Like Fluorescent Protein

The blue fluorescent protein (BFP)-like fluorescent protein of the present invention is a complex of the calcium-binding photoprotein and coelenteramide analogue of the present invention which is coordinated to the apoprotein of the photoprotein. That is, the BFP-like fluorescent protein of the present invention comprises coelenteramide analogue of the present invention, the apoprotein of the calcium-binding photoprotein and calcium ions or divalent or trivalent ions replaceable for the calcium ions. The BFP-like fluorescent protein can emit fluorescence upon excitation of light and can also generate luminescence upon contact of the BFP-like fluorescent protein with coelenterazine or its analogue.

According to the present invention, the BFP-like fluorescent protein is prepared from coelenteramide analogue of the present invention as follows. That is, coelenteramide analogue of the present invention is brought in contact with the apoprotein of the calcium-binding photoprotein in the presence of calcium ions or divalent or trivalent ions replaceable for the calcium ions thereby to obtain the BFP-like fluorescent protein. As used herein, the term “contact” means that the apoprotein and coelenteramide analogue are allowed to be present in the same reaction system, and includes, for example, addition of the apoprotein to a container charged with coelenteramide analogue, addition of coelenteramide analogue to a container charged with the apoprotein, mixing of the apoprotein with coelenteramide analogue, and the like.

In the present invention, coelenteramide analogue of the present invention used to produce the BFP-like fluorescent protein is the same as described above. Examples of coelenteramide analogue of the present invention include compounds prepared in EXAMPLES below or by methods modified therefrom.

The divalent or trivalent ions replaceable for the calcium ions which are used in the present invention to produce the BFP-like fluorescent protein are divalent or trivalent ions which trigger the luminescence reaction when they react with the calcium-binding photoprotein, in place of calcium ions. In other words, they refer to ions that exert the function similar to calcium ions on the calcium-binding photoprotein. Examples of the calcium ions or divalent or trivalent ions replaceable for the calcium ions include calcium ions (Ca²⁺), magnesium ions (Mg²⁺), strontium ions (Sr²⁺), barium ions (Ba²⁺), lead ions (Pb²⁺), cobalt ions (Co²⁺), nickel ions (Ni²⁺), cadmium ions (Cd²⁺), yttrium ions (Y³⁺), lanthanum ions (La³⁺), samarium ions (Sm³⁺), europium ions (Eu³⁺), dysprosium ions (Dy³⁺), thulium ions (Tm³⁺), ytterbium ions (Yb³⁺), and the like. Among these ions, the divalent metal ions are preferred, more preferably the divalent metal ions other than transition metals, e.g., Ca²⁺, Sr²⁺, Pb²⁺, etc.

In the present invention, the apoprotein of the calcium-binding photoprotein used to produce the BFP-like fluorescent protein is the same as described above.

The amount of coelenteramide analogue of the present invention used to produce the BFP-like fluorescent protein is not particularly limited and is in a range of, e.g., 1 mol to 5 mol, preferably 1 mol to 2 mol, more preferably 1 mol to 1.2 mol, based on 1 mol of apoprotein.

In the production of the BFP-like fluorescent protein, preferably coelenteramide analogue of the present invention is reacted with the apoprotein and calcium ions or divalent or trivalent ions replaceable for the calcium ions in the presence of a reducing agent. Examples of the reducing agent used herein include dithiothreitol (DTT), mercaptoethanol, etc. The amount of the reducing agent used to produce the BFP-like fluorescent protein is not particularly limited so long as the amount does not affect the regeneration of the BFP-like fluorescent protein, and the concentration is preferably sufficient to prevent the S—S bonds formed by the presence of cysteine residues at the three positions of apoaequorin. Such a concentration is, for example, 1 mM dithiothreitol or 0.1% (v/v) mercaptoethanol in a final concentration.

In the method for producing the BFP-like fluorescent protein, the reaction temperature and reaction time are not particularly limited but are generally at 0° C. to 42° C. for 0.1 to 2 hours, at 4° C. to 37° C. for 0.1 to 2 hours, or at 4° C. to 15° C. for 0.1 to 24 hours.

The BFP-like fluorescent protein thus produced may be further purified. Purification of the BFP-like fluorescent protein can be performed in a conventional manner of separation/purification. The separation/purification includes, for example, precipitation with ammonium sulfate, gel filtration chromatography, ion exchange chromatography, affinity chromatography, reversed phase high performance liquid chromatography, dialysis, ultrafiltration, etc., alone or in an appropriate combination of these techniques.

7.1.2. Use of Blue Fluorescent Protein (BFP)-Like Fluorescent Protein

(1) Use as a Luminescent Catalyst

The BFP-like fluorescent protein of the present invention acts on a luminescence substrate to emit light from the substrate and can be used as a luminescent catalyst. Therefore, the present invention provides a method for emitting light, which comprises contacting the BFP-like fluorescent protein of the present invention with coelenterazine or its analogues. As used herein, the term “contact” means that the BFP-like fluorescent protein and coelenterazine or its analogue are allowed to be present in the same reaction system, and includes, for example, addition of the BFP-like fluorescent protein to a container charged with coelenterazine or its analogue, addition of coelenterazine or its analogue to a container charged with the BFP-like fluorescent protein, mixing of the BFP-like fluorescent protein with coelenterazine or its analogue, and the like.

The luminescent substrate used in the method for light emission according to the present invention is, for example, coelenterazine or its analogue. The analogue of coelenterazine includes the same as described above.

These coelenterazine and analogues thereof are brought in contact with the BFP-like fluorescent protein. By the catalytic action of the BFP-like fluorescent protein contacted, coelenterazine or its analogue is oxidized to the corresponding coelenteramide or its analogue, whereby luminescence generates (at this time carbon dioxide is released). The luminescence time is generally 0.5 to 3 hours. However, the luminescence time can be further prolonged or more shortened, depending upon conditions chosen.

(2) Use as a Reporter Protein

The BFP-like fluorescent protein of the present invention can also be used as a reporter protein to determine the transcription activity of a promoter, etc. A polynucleotide encoding the apoprotein is fused to a target promoter or other expression control sequence (e.g., an enhancer, etc.) to construct a vector. The vector described above is transfected to a host cell. Coelenteramide analogue of the present invention and calcium ions or divalent or trivalent ions replaceable for the calcium ions are brought in contact with the host cell. By detecting the fluorescence from the fluorescent protein of the present invention, the activity of the target promoter or other expression control sequence can be determined. As used herein, the term “contact” means that a host cell and coelenteramide analogue as well as the calcium ions or divalent or trivalent ions replaceable for the calcium ions are allowed to be present in the same culture/reaction system, and includes, for example, addition of coelenteramide analogue and calcium ions or divalent or trivalent ions replaceable for the calcium ions to a culture container charged with a host cell, mixing of a host cell with coelenteramide analogue and calcium ions or divalent or trivalent ions replaceable for the calcium ions, culture of a host cell in the presence of coelenteramide analogue and calcium ions or divalent or trivalent ions replaceable for the calcium ions, and the like.

(3) Use as a Detection Marker

The BFP-like fluorescent protein of the present invention can be used as a marker for detection by fluorescence. The detection marker of the present invention can be used to detect a target substance in, e.g., immunoassay, hybridization assay, etc. The BFP-like fluorescent protein of the present invention can be used in the form bound to a target substance (protein, nucleic acid, etc.) in a conventional manner including chemical modification. Detection methods using the detection marker can be performed in a conventional manner.

The detection marker of the present invention can also be used to determine the distribution of a target substance by expressing the marker, e.g., as a fusion protein of the apoprotein and the target substance, then inserting the fusion protein into cells by means of microinjection or the like, and contacting them with coelenteramide analogue of the present invention and calcium ions or divalent or trivalent ions replaceable for the calcium ions. As used herein, the term “contact” means that cells and coelenteramide analogue as well as calcium ions or divalent or trivalent ions replaceable for the calcium ions are allowed to be present in the same culture/reaction system, and includes, for example, addition of coelenteramide analogue and calcium ions or divalent or trivalent ions replaceable for the calcium ions to a culture container charged with cells, mixing of cells with coelenteramide analogue and calcium ions or divalent or trivalent ions replaceable for the calcium ions, culture of a host cell in the presence of coelenteramide analogue and calcium ions or divalent or trivalent ions replaceable for the calcium ions, and the like.

The distribution of such a target protein, etc. can be determined by a method for detection such as fluorescence imaging. The apoprotein can also be used after expression in cells, in addition to the insertion into cells by means of microinjection, etc.

(4) Material for Amusement Supplies

When excited with light, the BFP-like fluorescent protein of the invention emits fluorescence. Therefore, the BFP-like fluorescent protein of the present invention can be preferably used as a fluorescence material for amusement supplies. Examples of such amusement supplies are fluorescent soap bubbles, fluorescent ice, fluorescent candies, fluorescent color paints, etc. The amusement supplies of the invention can be prepared in a conventional manner.

(5) Fluorescence Resonance Energy Transfer (FRET) Method

The BFP-like fluorescent protein of the present invention can be used for analyses including an analysis of biological functions, an assay (a determination) for enzyme activities, etc., based on the principle of intermolecular interaction by the fluorescence resonance energy transfer (FRET) method.

For example, using the BFP-like fluorescent protein of the invention as a donor or an acceptor and an organic compound or another fluorescent protein as an acceptor or a donor, the interaction between the proteins can be detected by causing fluorescence resonance energy transfer (FRET) between them. In some embodiments of the present invention, the organic compound used as an acceptor or a donor is Hoechist 3342, Indo-1, DAP1, etc. In some other embodiments of the present invention, another fluorescent protein used as an acceptor or a donor is another green fluorescent protein (GFP), another blue fluorescent protein (BFP), another mutant GFP fluorescent protein, phycobilin, etc. In a preferred embodiment of the present invention, the physiological functions to be analyzed include an orphan receptor (in particular, G-protein conjugated receptor), apoptosis, transcription regulation by gene expression, etc. In a preferred embodiment of the present invention, the enzyme to be analyzed is protease, esterase, kinase, etc.

Analysis of the physiological functions by the FRET method may be performed by known methods, for example, by modifications of the methods described in Hoffmann, C. et al Nat Methods (2005) 2: 171-176, Paulsson, J. F. et al. Exp. Diabetes Res. 2008: 2008, 865850, etc. Assay for the enzyme activity may also be performed by known methods, for example, by modifications of the methods described in Ting, A. Y. et al (2001) Proc. Natl. Acad. Sci. USA 98: 15003-15008, Evellin, S. et al (2004) Methods. Mol. Biol. 284: 259-270, Palmer A. E. & Tsien, R. Y. (2006) 1:1057-1065, etc.

Still, the present invention provides a kit used for the analysis method described above. The kit comprises the BFP-like fluorescent protein of the present invention and the organic compound and/or the fluorescent protein. Reagent such as the BFP-like fluorescent protein of the present invention, organic compounds, other fluorescent proteins, etc. may be dissolved in a suitable solvent and prepared to be suitable for storage. The solvent which may be used is at least one selected from the group consisting of water, ethanol, various buffer solutions, and the like. The kit may additionally comprise, if necessary, at least one selected from the group consisting of a container designed therefor, other necessary accessories and an instruction manual, and the like.

7.2. Green Fluorescent Protein (gFP)-Like Protein

7.2.1. Production of Green Fluorescent Protein (gFP)-Like Protein

The green fluorescent protein (gFP)-like protein of the present invention is a complex of the calcium-binding photoprotein and coelenteramide analogue of the present invention which is coordinated to the apoprotein of the photoprotein. That is, the gFP-like protein of the present invention comprises coelenteramide analogue of the present invention and the apoprotein of the calcium-binding photoprotein. On the other hand, the gFP-like protein of the present invention does not comprise calcium ions or divalent or trivalent ions replaceable for the calcium ions. The gFP-like protein can emit fluorescence upon excitation of light.

The gFP-like protein of the present invention can be produced by contacting coelenteramide analogue of the present invention with the apoprotein of the calcium-binding photoprotein in the presence of a chelating agent for removing calcium ions or divalent or trivalent ions replaceable for the calcium ions thereby to obtain the gFP-like protein.

Alternatively, the gFP-like protein can also be produced by removing calcium ions or divalent or trivalent ions replaceable for the calcium ions from the BFP-like fluorescent protein above to obtain the gFP-like protein. The calcium ions or divalent or trivalent ions replaceable for the calcium ions can be removed from the BFP-like fluorescent protein by treating with a chelating agent for sequestering calcium ions or divalent or trivalent ions replaceable for the calcium ions.

The chelating agent used to produce the gFP-like protein in the present invention may be any agent but is not particularly limited, so long as it strongly binds to calcium ions or divalent or trivalent ions replaceable for the calcium ions. Examples of the chelating agent include ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA), N-(2-hydroxyethyl)iminodiacetic acid (HIDA) and the like. As used herein, the calcium ions or divalent or trivalent ions replaceable for the calcium ions are the same as those described above.

The amount of the chelating agent used to produce the gFP-like fluorescent protein is not particularly limited unless its concentration affects regeneration of the gFP-like fluorescent protein. Since it is demonstrated that 3 mols of calcium ions bind to 1 mol of ion apoaequorin, e.g., 3 mols or more are preferred.

In the method for producing the gFP-like protein, the reaction temperature and reaction time are not particularly limited but are generally at 0° C. to 42° C. for 0.1 to 2 hours, at 4° C. to 37° C. for 0.1 to 2 hours, or at 4° C. to 15° C. for 0.1 to 24 hours.

The gFP-like protein thus obtained may be further purified. Purification of the gFP-like protein can be performed in a conventional manner of separation/purification. The separation/purification includes, for example, precipitation with ammonium sulfate, gel filtration chromatography, ion exchange chromatography, affinity chromatography, reversed phase high performance liquid chromatography, dialysis, ultrafiltration, etc., alone or in an appropriate combination of these techniques.

7.2.2. Use of Green Fluorescent Protein (gFP)-Like Protein

(1) Use as a Reporter Protein

The gFP-like protein of the present invention can also be used as a reporter protein to determine the transcription activity of a promoter, etc. A polynucleotide encoding the apoprotein is fused to a target promoter or other expression control sequence (e.g., an enhancer, etc.) to construct a vector. The vector described above is transfected to a host cell. Coelenteramide analogue of the present invention is brought in contact with the host cell to produce the BFP-like protein, which is then brought in contact with the chelating agent for removing calcium ions or divalent or trivalent ions replaceable for the calcium ions, thereby to produce the gFP-like protein. By detecting the fluorescence from the gFP-like protein of the present invention, the activity of the target promoter or other expression control sequence can be determined.

(2) Use as a Detection Marker

The gFP-like protein of the present invention can be used as a detection marker by its fluorescence. The detection marker of the present invention can be used to detect a target substance in, e.g., immunoassay, hybridization assay, etc. The gFP-like protein of the present invention can be used in the form bound to a target substance (protein, nucleic acid, etc.) in a conventional manner, including chemical modification. Detection methods using the detection marker can be performed in a conventional manner. The detection marker of the present invention can also be used to determine the distribution of a target substance by expressing the marker, e.g., as a fusion protein of the apoprotein and the target substance, then inserting the fusion protein into cells by means of microinjection or the like. Coelenteramide analogue of the present invention is brought in contact therewith to produce the BFP-like protein, which is then brought in contact with the chelating agent for removing calcium ions or divalent or trivalent ions replaceable for the calcium ions to produce the gFP-like protein, and so on. The marker can thus be used to determine the distribution of the target protein described above. The distribution of such a target protein, etc. can be determined by a method for detection such as fluorescence imaging. The apoprotein can also be used after expression in cells, in addition to the insertion into cells by means of microinjection, etc.

(3) Material for Amusement Supplies

The gFP-like protein of the present invention can be preferably used as a fluorescent material for amusement supplies. Examples of such amusement supplies are fluorescent soap bubbles, fluorescent ice, fluorescent candies, fluorescent color paints, etc. The amusement supplies of the present invention can be prepared in a conventional manner.

(4) Fluorescence Resonance Energy Transfer (FRET) Method

The gFP-like fluorescent protein of the present invention can be used for analyses including an analysis of biological functions, an assay for enzyme activities, etc., based on the principle of intermolecular interaction by the fluorescence resonance energy transfer (FRET) method.

For example, using the gFP-like fluorescent protein of the invention as a donor or an acceptor and an organic compound or another fluorescent protein as an acceptor or a donor, the interaction between the proteins can be detected by causing fluorescence resonance energy transfer (FRET) between them. In some embodiments of the present invention, the organic compound used as an acceptor or a donor is Hoechist 3342, Indo-1, DAP1, etc. In some other embodiments of the present invention, another fluorescent protein used as an acceptor or a donor is another green fluorescent protein (GFP), another blue fluorescent protein (BFP), another mutant GFP fluorescent protein, phycobilin, etc. In a preferred embodiment of the present invention, the physiological functions to be analyzed include an orphan receptor (in particular, G-protein conjugated receptor), apoptosis, transcription regulation by gene expression, etc. In a preferred embodiment of the present invention, the enzyme to be analyzed is protease, esterase, kinase, etc.

Analysis of the physiological functions by the FRET method may be performed by known methods, for example, by modifications of the methods described in Hoffmann, C. et al Nat. Methods (2005) 2: 171-176, Paulsson, J. F. et al. Exp. Diabetes Res. 2008:2008, 865850, etc. Assay for the enzyme activity may be performed by known methods, for example, by modifications of the methods described in Ting, A. Y. et al (2001) Proc. Natl. Acad. Sci. USA 98: 15003-15008, Evellin, S. et al (2004) Methods. Mol. Biol. 284: 259-270, Palmer A. E. & Tsien, R. Y. (2006) 1:1057-1065, etc.

The present invention further provides a kit used for the analysis method described above. The kit comprises the gFP-like fluorescent protein of the present invention and the organic compound and/or another fluorescent protein. Reagent such as the gFP-like fluorescent protein of the present invention, organic compounds, other fluorescent proteins, etc. may be dissolved in a suitable solvent and prepared to be suitable for storage. The solvent which may be used is at least one selected from the group consisting of water, ethanol, various buffer solutions, and the like. The kit may additionally comprise, if necessary, at least one selected from the group consisting of a container designed therefor, other necessary accessories and an instruction manual, and the like.

All literatures and publications mentioned in this specification are herein incorporated in their entirety by reference into the specification, irrespective of their purposes. The disclosure of the specification, the claims, abstract and drawings of Japanese Application JP2010-088175 filed on Apr. 6, 2010, based upon which the present application claims the benefit of priority, are entirely incorporated herein by reference.

The objects, characteristics, advantages and of the present invention as well as the idea thereof are apparent to those skilled in the art from the descriptions given herein, and those skilled in the art can easily implement the present invention. It is to be understood that the best mode to carry out the invention and specific examples are to be taken as preferred embodiments of the present invention. These descriptions are only for illustrative and explanatory purposes and are not intended to restrict the invention thereto. It is further apparent to those skilled in the art that various modifications may be made based on the descriptions given herein within the intent and scope of the present invention disclosed herein.

EXAMPLES Synthesis Examples

Materials and Methods

(1) High Performance Liquid Chromatography (HPLC)

The purities of coelenterazine analogues and coelenteramide analogues were determined by a 1100 Series HPLC System manufactured by Agilent. The column used was a Lichrosorb RP-18 (5 μm, 4.0 mm i.d.×125 mm) manufactured by Merck Chemicals. Moving phase: gradient 60-100% methanol/0.1% aqueous TFA for 40 min; flow rate: 0.45 mL/min; detection: UV 225 nm; the amount of injected sample: 0.5 mg/5 mL in methanol/0.1% aqueous TFA=6/4.

(2) Chromatography

Thin layer chromatography (TLC) for analysis was performed on a glass plate (MERCK 5715, silica gel 60 F₂₅₄) previously coated with silica gel. The spots were detected under a UV lamp (254 nm or 365 nm) by adsorbing iodine, dipping in an aqueous anisaldehyde solution and charring on a hot plate. The unsaturated C—C bonds were detected by dipping in an aqueous potassium permanganate solution followed by charring on a hot plate.

For preparative flush column chromatography, silica gels (Kanto Chemical Co., Inc., 37563-85, silica gel 60 N (spherical, neutral), particle size 45-50 μm) and (Kanto Chemical Co., Inc., 37565-85, silica gel 60 N (spherical, neutral), particle size 63-210 μm) were used. For purification of the CTZ analogues, however, silica gels (Kanto Chemical Co., Inc., 37562-79, silica gel 60 N (spherical), particle size 40-50 μm) and (Kanto Chemical Co., Inc., 37558-79, silica gel 60 N (spherical), particle size 100-210 μm) were used.

(3) Nuclear Magnetic Resonance (NMR) Spectra

¹H Nuclear magnetic resonance (NMR) spectra (400 MHz) were determined on a Unity Plus 400 nuclear magnetic resonance apparatus manufactured by Varian, Inc. Chemical shifts (δ) were expressed as values relative to the peaks from tetramethylsilane ((CH₃)₄Si) (measured in CDCl₃; 0 ppm) or the peaks from non-deuterated solvent for analysis (measured in CD₃OD; 3.31 ppm, measured in DMSO-d₆; 2.49 ppm) as an internal standard. Abbreviations s, d and m used for the signal splitting patterns represent singlet, doublet and multiplet, respectively.

¹³C Nuclear magnetic resonance spectra (75.5 or 67.8 MHz) were determined by a Mercury 300 nuclear magnetic resonance apparatus manufactured by Varian, Inc., or on JNM-EX270 manufactured by JEOL. Chemical shifts (δ) were expressed as values relative to the peaks from carbon in the solvent for analysis (measured in acetone-d₆; 29.8 ppm, measured in DMSO-d₆; 39.5 ppm) as an internal standard.

(4) Infrared Absorption (IR) Spectra

IR spectra were determined by the diffuse reflection method using a SHIMADZU IR Prestige-21 spectrophotometer equipped with DRS-8000, manufactured by Shimadzu Corporation.

(5) Mass Spectrometry

High resolution mass spectrometry (HRMS) was performed by the electrospray ionization method (ESI⁺) with a Bruker micrOTOF manufactured by Bruker or by the fast atom bombardment method (FAB⁺) using JMS-700 manufactured by JEOL.

(6) Elemental Analysis

Elemental analysis (Anal.) was performed using YANACO CHN CORDER MT-5.

(7) Chemical Reagents

The reagents were all commercially available and used without further treatment unless otherwise indicated. The solvents for the reactions, extractions and chromatography were DMF, ethyl acetate, n-hexane, anhydrous THF, toluene, ethanol, DMSO, diethyl ether, methanol, THF, dichloromethane, 1,4-dioxane, anhydrous pyridine, diethylamine, anhydrous dichloromethane, anhydrous 1,2-dichloroethane and anhydrous DMF, all commercially available, and used without further treatment.

Mixing ratios of the solvents are based on volume, unless otherwise indicated.

The reaction reagents below were used. Imidazole (Cat. No. 095-0015), triisopropyl borate (Cat. No. 324-41535), Na₂CO₃ (Cat. No. 199-01585), aminopyrazine (Cat. No. 013-12083), N-bromosuccinimide (Cat. No. 025-07235), p-hydroxybenzaldehyde (Cat. No. 081-05925), triethylamine (Cat. No. 202-02646), methanesulfonyl chloride (Cat. No. 131-01583), 1-naphthaleneboronic acid (Cat. No. 322-63393), benzo[b]thiophene-2-boronic acid (Cat. No. 329-64121), p-nitrophenylboronic acid (Cat. No. 327-59813), hydrochloric acid (Cat. No. 080-01066), p-hydroxyphenylacetic acid (Cat. No. 084-04185), oxalyl dichloride (Cat. No. 155-01642), 4-(dimethylamino)pyridine (Cat. No. 042-19212), thionyl chloride (Cat. No. 200-01106) and m-anisoyl chloride (Cat. No. 326-77701), purchased from Wako Pure Chemical Co., Ltd., dichlorobis(triphenylphosphine) palladium (II) (Cat. No. 412740), 2-naphthaleneboronic acid (Cat. No. 480134), 2-(tributylstannyl)thiophene (Cat. No. 414492), thianaphthene-3-boronic acid (Cat. No. 512117), trans-2-phenylvinylboronic acid (Cat. No. 473790), 3-thienylboronic acid (Cat. No. 436844), 1-phenylvinylboronic acid (Cat. No. 571350), 4-(dimethylamino)phenylboronic acid (Cat. No. 483532), copper (I) iodide (Cat. No. 21554), phenylacetylene (Cat. No. 117706) and 1 M tetrabutylammonium fluoride in THF (Cat. No. 216143), purchased from Aldrich, Inc., 4-bromophenol (Cat. No. B0787), tert-butyldimethylsilyl chloride (Cat. No. B0995), 5-bromopyrazin-2-amine (Cat. No. A1683), ethyl diethoxyacetate (Cat. No. D1883), phenylboronic acid (Cat. No. B0857), thieno[3,2-b]thiophen-2-boronic acid (Cat. No. T2621), dithieno[3,2-b:2′,3′-d]thiophen-2-boronic acid (Cat. No. D3823), 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene (Cat. No. T2518), 4-methoxyphenyl isocyanate (Cat. No. I0440), 4-methoxyphenyl isothiocyanate (Cat. No. I0513) and 4-methoxybenzoyl chloride (Cat. No. M0721), purchased from Tokyo Chemical Industry Co., Ltd., 2.64 M n-butyl lithium in n-hexane (Cat. No. 04937-25), sodium borohydride (Cat. No. 37828-35), magnesium, turning (Cat. No. 26000-25), NH₄Cl (Cat. No. 01287-01) and sodium hydride (Cat. No. 37842-35), purchased from Kanto Chemical Co., Inc., and, palladium/charcoal activated (10% Pd) (Cat. 8.07104.0010) purchased from MERCK, Inc., were used without further treatment.

Reference Synthesis Example 1 (4-Bromophenoxy)(tert-butyl)dimethylsilane (36) (known compound, Reference: P. Jeanjot, et al., Synthesis, 513-522 (2003))

To a solution of 4-bromophenol (35) (20.0 g, 116 mmol) in DMF (200 mL) were successively added imidazole (23.6 g, 347 mmol) and tert-butyldimethylsilyl chloride (24.4 g, 162 mmol) at 0° C., and the mixture was stirred for 3 hours while elevating to room temperature. To the mixture was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (200 mL), and dried over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane/ethyl acetate=100/1) to give Compound 36 (32.3 g, crude) as a colorless oil. The product was used in the following reaction without further purification. R_(f)=0.57 (n-hexane/ethyl acetate=49/1); ¹H NMR (400 MHz, CDCl₃) δ 0.18 (s, 6H), 0.97 (s, 9H), 6.68-6.75 (AA′BB′, 2H), 7.30-7.35 (AA′BB′, 2H).

Reference Synthesis Example 2 4-(tert-Butyldimethylsilyloxy)phenylboronic acid (37) (known compound, Reference: P. Jeanjot, et al., Synthesis, 513-522 (2003))

Under an argon atmosphere, to a solution of (4-bromophenoxy)(tert-butyl)dimethylsilane (36) (32.3 g, crude) prepared above in anhydrous THF (300 mL) was added n-butyl lithium (2.64 M n-hexane solution) (46.0 mL, 121 mmol) at −78° C., and the mixture was stirred for an hour. To this was added triisopropyl borate (134 mL, 579 mmol) at the same temperature and the mixture was stirred for 13 hours while elevating to room temperature. To the mixture was added 1 M hydrochloric acid (200 mL) and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 37 (20.9 g, 82.9 mmol, 71.8% (2 steps)) as a colorless solid. R_(f)=0.62 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, CDCl₃) δ 0.25 (s, 6H), 1.01 (s, 9H), 6.93-6.98 (AA′BB′, 2H), 8.09-8.14 (AA′BB′, 2H).

Reference Synthesis Example 3 5-[4-(tert-Butyldimethylsilyloxy)phenyl]pyrazin-2-amine (39) (known compound)

Under an argon atmosphere, to a solution of 4-(tert-butyldimethylsilyloxy)phenylboronic acid (37) (7.97 g, 31.6 mmol) in toluene (290 mL) and ethanol (10 mL) were successively added 5-bromopyrazin-2-amine (38) (5.00 g, 28.7 mmol), dichlorobis(triphenylphosphine)palladium (II) (1.21 g, 1.72 mmol) and 1 M Na₂CO₃ aqueous solution (29.0 mL, 29.0 mmol) at room temperature, and the mixture was heated to reflux for 17 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane/ethyl acetate=2/1) to give Compound 39 (7.82 g, 25.9 mmol, 90.2%) as a colorless solid. R_(f)=0.39 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, CDCl₃) δ 0.22 (s, 6H), 1.00 (s, 9H), 4.53 (s, 2H), 6.88-6.95 (AA′BB′, 2H), 7.71-7.79 (AA′BB′, 2H), 8.04 (s, 1H), 8.84 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.0 (2C), 126.1 (2C), 130.7, 131.3, 138.1, 139.2, 154.5, 154.7; IR (KBr, cm⁻¹) 417, 478, 513, 544, 567, 629, 644, 658, 683, 750, 781, 806, 841, 912, 1007, 1052, 1080, 1103, 1169, 1207, 1254, 1341, 1379, 1418, 1474, 1506, 1539, 1570, 1605, 1639, 2857, 2893, 2928, 2955, 3163, 3302, 3431.

Reference Synthesis Example 4 3-Bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (known compound, Reference: F. D. Wael, et al., Bioorg. Med. Chem., 17, 4336-4344 (2009))

To a solution of 5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (39) (12.7 g, 42.1 mol) in DMSO (790 mL) and water (19.5 mL) was added N-bromosuccinimide (7.90 g, 44.4 mmol) at room temperature and the mixture was stirred for 17 hours. To the mixture was added water and the product was extracted with diethyl ether (400 mL×8). The combined organic extract was washed successively with water (300 mL×2) and brine (200 mL×2), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane/ethyl acetate=3/1) to give Compound 5 (13.0 g, 34.2 mmol, 80.9%) as a yellow solid. R_(f)=0.32 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, CDCl₃) δ 0.22 (s, 6H), 0.99 (s, 9H), 4.99 (s, 2H), 6.87-6.94 (AA′BB′, 2H), 7.71-7.77 (AA′BB′, 2H), 8.34 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.4 (3C), 120.1 (2C), 124.7, 126.4 (2C), 128.9, 137.4, 140.0, 152.0, 155.2; IR (KBr, cm⁻¹) 554, 619, 646, 675, 704, 756, 779, 806, 849, 905, 1036, 1094, 1109, 1169, 1202, 1261, 1337, 1416, 1464, 1501, 1566, 1605, 1630, 2857, 2928, 2955, 3138, 3281, 3460.

Reference Synthesis Example 5 3,5-Dibromopyrazin-2-amine (42) (known compound, Reference: P. Jeanjot, et al., Synthesis, 513-522 (2003))

To a solution of aminopyrazine (41) (10.0 g, 105 mmol) in DMSO (200 mL) and water (5 mL) was added N-bromosuccinimide (39.3 g, 221 mmol) at room temperature, and the mixture was stirred for 23 hours. To the mixture was added water and the product was extracted with diethyl ether (300 mL×4). The combined organic extract was washed successively with water (400 mL×2) and brine (500 mL×2), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 280 g, n-hexane/dichloromethane/ethyl acetate=5/4/1). The resulting solid was further purified by recrystallization (n-hexane/ethyl acetate) to give Compound 42 (17.3 g, 68.3 mmol, 64.9%) as a colorless solid. R_(f)=0.48 (n-hexane/dichloromethane/ethyl acetate=5/4/1); ¹H NMR (400 MHz, CDCl₃) δ 5.05 (s, 2H), 8.05 (s, 1H).

Reference Synthesis Example 6 4-(tert-Butyldimethylsilyloxy)benzaldehyde (44) (known compound, Reference: M. Adamczyk, et al., Tetrahedron, 59, 8129-8142 (2003))

To a solution of p-hydroxybenzaldehyde (43) (12.0 g, 98.3 mmol) in DMF (25 mL) was successively added imidazole (16.7 g, 245 mmol) and tert-butyldimethylsilyl chloride (17.8 g, 118 mmol) at 0° C., and the mixture was stirred for 3 hours while elevating to room temperature. To the mixture was added water and the product was extracted with ethyl acetate (200 mL×3). The organic layer was washed successively with saturated aqueous solution of K₂CO₃ (300 mL), water (300 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane/ethyl acetate=19/1) to give Compound 44 (20.5 g, 86.7 mmol, 88.2%) as a colorless oil. R_(f)=0.32 (n-hexane/ethyl acetate=19/1); ¹H NMR (400 MHz, CDCl₃) δ 0.25 (s, 6H), 1.00 (s, 9H), 6.92-6.98 (AA′BB′, 2H), 7.76-7.83 (AA′BB′, 2H), 9.89 (s, 1H).

Reference Synthesis Example 7 4-(tert-Butyldimethylsilyloxy)benzyl alcohol (45) (known compound, Reference: M. Adamczyk, et al., Tetrahedron, 59, 8129-8142 (2003))

To a solution of 4-(tert-butyldimethylsilyloxy)benzaldehyde (44) (20.5 g, 86.7 mmol) in methanol (120 mL) was added sodium borohydride (3.93 g, 104 mmol) at 0° C., and the mixture was stirred for 5 hours while elevating to room temperature. To the mixture was added water and the product was extracted with diethyl ether (300 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. The residue was filtered and concentrated under reduced pressure to give Compound 45 (20.5 g, 104 mmol, 100%) as a colorless oil. The product has a sufficient purity and used in the following reaction without further purification. R_(f)=0.21 (n-hexane/ethyl acetate=19/1); ¹H NMR (400 MHz, CDCl₃) δ 0.19 (s, 6H), 0.98 (s, 9H), 1.59 (br, 1H), 4.61 (s, 2H), 6.80-6.85 (AA′BB′, 2H), 7.20-7.26 (AA′BB′, 2H).

Reference Synthesis Example 8 4-(tert-Butyldimethylsilyloxy)benzyl chloride (46) (known compound, Reference: M. Adamczyk, et al., Tetrahedron, 59, 8129-8142 (2003))

To a solution of 4-(tert-butyldimethylsilyloxy)benzyl alcohol (45) (10.0 g, 42.0 mmol) in DMF (100 mL) were successively added triethylamine (12.0 mL, 86.1 mmol) and methanesulfonyl chloride (4.90 mL, 63.1 mmol) at 0° C., and the mixture was stirred for 20 hours while elevating to room temperature. To the mixture was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane/diethyl ether=10/1) to give Compound 46 (8.07 g, 31.4 mmol, 74.9%) as a colorless oil. R_(f)=0.71 (n-hexane/ethyl acetate=19/1); ¹H NMR (400 MHz, CDCl₃) δ 0.20 (s, 6H), 0.98 (s, 9H), 4.56 (s, 2H), 6.78-6.84 (AA′BB′, 2H), 7.22-7.27 (AA′BB′, 2H).

Reference Synthesis Example 9 3-[4-(tert-Butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (known compound, Reference: M. Adamczyk, et al., Tetrahedron, 59, 8129-8142 (2003))

Magnesium turnings (640 mg, 26.3 mmol) were placed in a reaction flask and dried in vacuo by heating with a heat gun. The flask were then allowed to cool to room temperature and filled with a dry argon atmosphere. To this was added anhydrous THF (28 mL) and to the mixture was added dropwise 4-(tert-butyldimethylsilyloxy)benzyl chloride (46) (6.15 g, 24.0 mmol) at room temperature. The mixture was stirred at room temperature for an hour while the most of the magnesium turnings disappeared affording a THF solution of 4-(tert-butyldimethylsilyloxy)benzyl magnesium chloride, which was used in the following reaction without further treatment.

Under an argon atmosphere, to a solution of ethyl diethoxyacetate (4.30 mL, 24.0 mmol) in anhydrous THF (50 mL) was added the THF solution of 4-(tert-butyldimethylsilyloxy)benzyl magnesium chloride prepared above at −78° C. The mixture was stirred at −78° C. for 2 hours and an aqueous 10% NH₄Cl solution (150 mL) was added thereto. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with a 10% NH₄Cl aqueous solution (300 mL), water (300 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane/ethyl acetate=40/1) to give Compound 8 (6.19 g, 17.6 mmol, 72.9%) as a colorless oil. R_(f)=0.43 (n-hexane/ethyl acetate=19/1); ¹H NMR (400 MHz, CDCl₃) δ 0.18 (s, 6H), 0.97 (s, 9H), 1.24 (t, 6H, J=7.1 Hz), 3.53 (dq, 2H, J=2.3, 7.1 Hz), 3.68 (dq, 2H, J=2.3, 7.1 Hz), 4.63 (s, 1H), 6.74-6.81 (AA′BB′, 2H), 7.03-7.10 (AA′BB′, 2H).

Reference Synthesis Example 10 2-[4-(tert-Butyldimethylsilyloxy)phenyl]acetic acid (9) (known compound, Reference: O. Brummer, et al., Tetrahedron Lett., 42, 2257-2259 (2001))

To a solution of p-hydroxyphenylacetic acid (48) (10.0 g, 65.7 mmol) in THF (80 mL) were successively added imidazole (22.4 g, 329 mmol) and tert-butyldimethylsilyl chloride (27.7 g, 184 mmol) at 0° C., and the mixture was stirred for an hour while elevating to room temperature. To this was added a solution of saturated Na₂CO₃ (250 mL) and the mixture was stirred at room temperature for an hour. To the mixture was added 2 M HCl aqueous solution (650 mL) and the product was extracted with ethyl acetate (300 mL×3). The combined organic extract was washed successively with water (400 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 200 g, n-hexane→n-hexane/ethyl acetate/acetic acid=1/1/0.05) to give Compound 9 (10.6 g, 39.9 mmol, 60.7%) as a colorless solid. R_(f)=0.64 (n-hexane/ethyl acetate=1/2); ¹H NMR (400 MHz, CDCl₃) δ 0.20 (s, 6H), 0.99 (s, 9H), 3.58 (s, 2H), 6.76-6.85 (AA′BB′, 2H), 7.10-7.17 (AA′BB′, 2H).

Synthesis Example 1

Coelenterazine (CTZ) analogues modified at the C-8 position

1-1) TMD-296 (3a)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-phenylpyrazin-2-amine (7a)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.50 g, 3.94 mmol) in toluene (45 mL) and ethanol (1.7 mL) were successively added phenylboronic acid (6a) (577 mg, 4.73 mmol), dichlorobis(triphenylphosphine)palladium (II) (165 mg, 235 μmol) and 1 M Na₂CO₃ aqueous solution (4.00 mL, 4.00 mmol) at room temperature, and the mixture was heated to reflux for 17 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7a (1.46 g, 3.87 mmol, 98.1%) as a brown solid. R_(f)=0.41 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.21 (s, 6H), 0.96 (s, 9H), 6.20 (s, 2H), 6.89-6.94 (AA′BB′, 2H), 7.42-7.55 (m, 3H), 7.76-7.82 (m, 2H), 7.85-7.91 (AA′BB′, 2H), 8.48 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.0 (2C), 126.4 (2C), 128.2 (2C), 128.4, 128.6 (2C), 130.5, 137.2, 137.68, 137.72, 139.9, 151.6, 155.0; IR (KBr, cm⁻¹) 523, 637, 677, 700, 720, 752, 779, 808, 841, 914, 1018, 1070, 1092, 1105, 1167, 1204, 1263, 1319, 1362, 1381, 1435, 1460, 1510, 1605, 2857, 2886, 2928, 2955, 3059, 3159, 3291, 3428; HRMS (ESI⁺) m/z 378.1990 ([M+H]⁺, C₂₂H₂₈N₃OSi⁺ requires 378.1996).

2-(4-Hydroxybenzyl)-6-(4-hydroxyphenyl)-8-phenylimidazo[1,2-a]pyrazin-3(7H)-one (3a, TMD-296)

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-phenylpyrazin-2-amine (7a) (272 mg, 720 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (381 mg, 1.08 mmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (780 μL) at 0° C., and the mixture was heated to reflux for 17 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3a (TMD-296) (158 mg, 386 μmol, 53.6%) as an orange solid. R_(f)=0.59 (ethyl acetate); HPLC retention time 8.0 min; ¹H NMR (400 MHz, CD₃OD) δ 4.16 (s, 2H), 6.69-6.76 (AA′BB′, 2H), 6.91-6.97 (AA′BB′, 2H), 7.09-7.16 (AA′BB′, 2H), 7.56-7.68 (m, 3H), 7.84-7.91 (AA′BB′, 2H), 7.98-8.03 (m, 2H), 8.39 (s, 1H); IR (KBr, cm⁻¹) 523, 656, 696, 779, 843, 891, 1173, 1265, 1342, 1443, 1512, 1591, 1609, 1655, 2814, 3154; HRMS (ESI⁺) m/z 410.1497 ([M+H]⁺, C₂₅H₂₀N₃O₃ ⁺ requires 410.1499).

1-2) TMD-282 (3b)

(E)-5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-styrylpyrazin-2-amine (7b)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.00 g, 2.63 mmol) in toluene (30 mL) and ethanol (1.2 mL) were successively added trans-2-phenylvinylboronic acid (6b) (543 mg, 3.16 mmol), dichlorobis(triphenylphosphine)palladium (II) (111 mg, 158 μmol) and 1 M Na₂CO₃ aqueous solution (2.70 mL, 2.70 mmol) at room temperature, and the mixture was heated to reflux for 18 hours. After cooling to room temperature, to the mixture was added water, and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7b (997 mg, 2.47 mmol, 94.0%) as a yellow solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.19 (s, 6H), 0.94 (s, 9H), 6.60 (s, 2H), 6.84-6.91 (AA′BB′, 2H), 7.22-7.31 (m, 1H), 7.31-7.44 (m, 2H), 7.55 (d, 1H, J=16 Hz), 7.65-7.77 (m, 3H), 7.87-7.93 (AA′BB′, 2H), 9.39 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.1 (2C), 122.1, 126.5 (2C), 127.3 (2C), 128.2, 128.7 (2C), 130.8, 132.8, 133.8, 136.9, 137.7, 139.4, 152.0, 155.0; IR (KBr, cm⁻¹) 444, 463, 507, 534, 633, 691, 745, 781, 806, 841, 914, 964, 1011, 1072, 1088, 1103, 1153, 1213, 1263, 1379, 1420, 1454, 1512, 1566, 1605, 1634, 2856, 2886, 2930, 2955, 3057, 3196, 3329; HRMS (ESI⁺) m/z 404.2161 ([M+H]⁺, C₂₄H₃₀N₃OSi⁺ requires 404.2153).

(E)-2-(4-Hydroxybenzyl)-6-(4-hydroxyphenyl)-8-styrylimidazo[1,2-a]pyrazin-3(7H)-one (3b, TMD-282)

Under an argon atmosphere, to a mixture of (E)-5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-styrylpyrazin-2-amine (7b) (290 mg, 719 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (380 mg, 1.08 mmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (600 μL) at, 0° C. and the mixture was heated to reflux for 15 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3b (TMD-282) (74.0 mg, 170 μmol, 23.6%) as a brown solid. R_(f)=0.22 (ethyl acetate); HPLC retention time 14.3 min.

1-3) TMD-276 (3d)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(naphthalen-1-yl)pyrazin-2-amine (7d)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.48 g, 3.90 mmol) in toluene (45 mL) and ethanol (2 mL) were successively added 1-naphthaleneboronic acid (6d) (805 mg, 4.68 mmol), dichlorobis(triphenylphosphine)palladium (II) (164 mg, 234 μmol) and 1 M Na₂CO₃ aqueous solution (4.00 mL, 4.00 mmol) at room temperature, and the mixture was heated to reflux for 18 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=4/1) to give Compound 7d (1.44 g, 3.37 mmol, 86.5%) as a yellow foamy solid. R_(f)=0.25 (n-hexane/ethyl acetate=4/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.14 (s, 6H), 0.90 (s, 9H), 5.89 (s, 2H), 6.80-6.87 (AA′BB′, 2H), 7.41-7.48 (m, 1H), 7.48-7.64 (m, 4H), 7.74-7.81 (AA′BB′, 2H), 7.96-8.04 (m, 2H), 8.55 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.1 (2C), 125.2, 125.8, 126.0, 126.37 (2C), 126.40, 127.2, 128.4, 128.8, 130.6, 130.9, 133.6, 134.7, 137.8, 138.1, 139.5, 152.5, 154.9; IR (KBr, cm⁻¹) 517, 544, 579, 631, 675, 706, 739, 777, 806, 841, 910, 980, 1055, 1080, 1103, 1121, 1169, 1179, 1198, 1265, 1337, 1362, 1375, 1423, 1450, 1508, 1570, 1605, 2857, 2886, 2928, 2955, 3051, 3179, 3300, 3383, 3474; HRMS (ESI⁺) 428.2163 ([M+H]⁺, C₂₆H₃₀N₃OSi⁺ requires 428.2153).

2-(4-Hydroxybenzyl)-6-(4-hydroxyphenyl)-8-(naphthalen-1-yl)imidazo[1,2-a]pyrazin-3(7H)-one (3d, TMD-276)

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(naphthalen-1-yl)pyrazin-2-amine (7d) (255 mg, 596 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (315 mg, 894 μmol) dissolved in 1,4-dioxane (2 mL) was added, 4 M hydrochloric acid (780 μL) at 0° C. and the mixture was heated to reflux for 15 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3d (TMD-276) (74.3 mg, 162 μmol, 27.1%) as an orange solid. R_(f)=0.54 (ethyl acetate/methanol=20/1); HPLC retention time 9.1 min; ¹H NMR (400 MHz, CD₃OD) δ 4.06 (s, 2H), 6.64-6.70 (AA′BB′, 2H), 6.88-6.95 (AA′BB′, 2H), 7.00-7.07 (AA′BB′, 2H), 7.47-7.55 (m, 1H), 7.55-7.63 (m, 1H), 7.68-7.73 (m, 1H), 7.80-7.92 (m, 4H, includes AA′BB′), 8.00-8.07 (m, 1H), 8.14-8.22 (m, 1H), 8.54 (s, 1H); IR (KBr, cm⁻¹) 463, 492, 646, 779, 808, 968, 1015, 1045, 1082, 1109, 1173, 1240, 1325, 1346, 1443, 1508, 1591, 1609, 1653, 2814, 3169; HRMS (ESI⁺) m/z 460.1656 ([M+H]⁺, C₂₉H₂₂N₃O₃ ⁺ requires 460.1656).

1-4) TMD-277 (3e)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(naphthalen-2-yl)pyrazin-2-amine (7e)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.00 g, 2.63 mmol) in toluene (30 mL) and ethanol (1.2 mL) were successively added 2-naphthaleneboronic acid (6e) (543 mg, 3.16 mmol), dichlorobis(triphenylphosphine)palladium (II) (110 mg, 157 μmol) and 1 M Na₂CO₃ aqueous solution (2.70 mL, 2.70 mmol) at room temperature, and the mixture was heated to reflux for 15 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7e (1.04 g, 2.43 mmol, 92.2%) as a yellow solid. R_(f)=0.33 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.92 (s, 9H), 6.32 (s, 2H), 6.85-6.92 (AA′BB′, 2H), 7.49-7.57 (m, 2H), 7.84-7.91 (m, 3H, includes AA′BB′), 7.91-7.96 (m, 1H), 7.97-8.03 (m, 2H), 8.31 (s, 1H), 8.47 (s, 1H); IR (KBr, cm⁻¹) 419, 438, 530, 648, 669, 698, 743, 779, 814, 841, 918, 939, 1009, 1103, 1126, 1165, 1192, 1219, 1252, 1341, 1362, 1389, 1420, 1431, 1462, 1508, 1530, 1566, 1605, 1636, 2859, 2895, 2930, 2955, 3038, 3057, 3159, 3296, 3416; HRMS (ESI⁺) m/z 428.2155 ([M+H]⁺, C₂₆H₃₀N₃OSi⁺ requires 428.2153).

2-(4-Hydroxybenzyl)-6-(4-hydroxyphenyl)-8-(naphthalen-2-yl)imidazo[1,2-a]pyrazin-3(7H)-one (3e, TMD-277)

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(naphthalen-2-yl)pyrazin-2-amine (7e) (308 mg, 720 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (381 mg, 1.08 mmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (600 μL) at 0° C., and the mixture was heated to reflux for 14 hours. After cooling to room temperature the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3e (TMD-277) (89.9 mg, 196 μmol, 27.2%) as an orange solid. R_(f)=0.59 (ethyl acetate/methanol=20/1); HPLC retention time 13.6 min; ¹H NMR (400 MHz, CD₃OD) δ 4.17 (s, 2H), 6.70-6.77 (AA′BB′, 2H), 6.91-6.98 (AA′BB′, 2H), 7.11-7.17 (AA′BB′, 2H), 7.56-7.68 (m, 2H), 7.88-7.94 (AA′BB′, 2H), 7.95-8.00 (m, 1H), 8.01-8.06 (m, 1H), 8.08-8.11 (m, 2H), 8.37 (s, 1H), 8.55 (s, 1H); IR (KBr, cm⁻¹) 480, 552, 656, 752, 822, 903, 1111, 1173, 1242, 1269, 1356, 1447, 1513, 1558, 1611, 1653, 2814, 2897, 3165; HRMS (ESI⁺) m/z 460.1666 ([M+H]⁺, C₂₉H₂₂N₃O₃ ⁺ requires 460.1656).

1-5) TMD-278 (3f)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(thiophen-2-yl)pyrazin-2-amine (7f)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.20 g, 3.15 mmol) in 1,4-dioxane (30 mL) were successively added 2-(tributylstannyl)thiophene (60 (1.10 mL, 3.46 mmol) and dichlorobis(triphenylphosphine)palladium (II) (111 mg, 158 μmol) at room temperature, and the mixture was heated to reflux for 14 hours. After cooling to room temperature, to the mixture was added saturated KF aqueous solution and the mixture was stirred at room temperature for 30 minutes. The metal catalyst was removed by filtration, and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with saturated KF aqueous solution (300 mL), water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7f (1.03 g, 2.68 mmol, 84.9%) as a yellow solid. R_(f)=0.33 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.19 (s, 6H), 0.94 (s, 9H), 6.42 (s, 2H), 6.87-6.94 (AA′BB′, 2H), 7.17 (dd, 1H, J=3.8, 5.2 Hz), 7.65 (d, 1H, J=5.2 Hz), 7.74 (d, 1H, J=3.8 Hz), 7.83-7.91 (AA′BB′, 2H), 8.46 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.1 (2C), 125.6, 126.4 (2C), 128.2, 128.3, 129.9, 131.8, 136.9, 139.5, 142.6, 149.8, 155.2; IR (KBr, cm⁻¹) 471, 509, 536, 581, 623, 646, 669, 716, 741, 779, 804, 822, 839, 912, 1011, 1057, 1082, 1111, 1172, 1202, 1263, 1279, 1360, 1379, 1435, 1454, 1477, 1512, 1564, 1607, 2857, 2895, 2930, 2953, 3335, 3439; HRMS (ESI⁺) m/z 384.1551 ([M+H]⁺, C₂₀H₂₆N₃OSSi⁺ requires 384.1560). 2-(4-Hydroxybenzyl)-6-(4-hydroxyphenyl)-8-(thiophen-2-yl)imidazo[1,2-a]pyrazin-3(7H)-one (3f, TMD-278)

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thiophen-2-yl)pyrazin-2-amine (7f) (276 mg, 720 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (381 mg, 1.08 mmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (780 μL) at 0° C. and the mixture was heated to reflux for 16 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3f (TMD-278) (68.2 mg, 164 μmol, 22.8%) as a brown solid. R_(f)=0.67 (ethyl acetate/methanol=20/1); HPLC retention time 9.5 min; ¹H NMR (400 MHz, CD₃OD) δ 4.22 (s, 2H), 6.72-6.78 (AA′BB′, 2H), 6.90-6.97 (AA′BB′, 2H), 7.11-7.18 (AA′BB′, 2H), 7.32 (dd, 1H, J=3.8, 5.2 Hz), 7.87 (dd, 1H, J=1.1, 5.2 Hz), 7.91-7.97 (AA′BB′, 2H), 8.12 (dd, 1H, J=1.1, 3.8 Hz), 8.48 (s, 1H); IR (KBr, cm⁻¹) 521, 581, 629, 721, 777, 841, 881, 966, 1109, 1172, 1261, 1341, 1429, 1508, 1533, 1609, 1653, 2822, 3107; HRMS (ESI⁺) m/z 416.1075 ([M+H]⁺, C₂₃H₁₈N₃O₃S⁺ requires 416.1063).

1-6) TMD-336 (3g)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(thiophen-3-yl)pyrazin-2-amine (7g)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.50 g, 3.94 mmol) in toluene (45 mL) and ethanol (1.8 mL) were successively added 3-thienylboronic acid (6g) (605 mg, 4.73 mmol), dichlorobis(triphenylphosphine)palladium (II) (165 mg, 235 μmol) and 1 M Na₂CO₃ aqueous solution (4.00 mL, 4.00 mmol) at room temperature and the mixture was heated to reflux for 15 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 150 g, n-hexane/ethyl acetate=3/1) to give Compound 7g (1.19 g, 3.11 mmol, 78.9%) as a red solid. R_(f)=0.50 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.21 (s, 6H), 0.96 (s, 9H), 6.29 (s, 2H), 6.88-6.96 (AA′BB′, 2H), 7.66-7.73 (m, 2H), 7.88-7.93 (AA′BB′, 2H), 8.06-8.09 (m, 1H), 8.47 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.5 (2C), 17.9, 25.5 (3C), 120.1 (2C), 124.7, 126.1, 126.4 (2C), 128.2, 130.4, 133.5, 136.7, 138.7, 139.6, 151.2, 155.0; IR (KBr, cm⁻¹) 511, 534, 551, 635, 662, 694, 719, 737, 754, 779, 808, 843, 916, 1009, 1034, 1086, 1103, 1167, 1182, 1196, 1215, 1260, 1331, 1366, 1389, 1408, 1454, 1510, 1566, 1605, 2857, 2886, 2928, 2953, 3038, 3115, 3175, 3289, 3412; HRMS (ESI⁺) m/z 384.1560 ([M+H]⁺, C₂₀H₂₆N₃OSSi⁺ requires 384.1560).

2-(4-Hydroxybenzyl)-6-(4-hydroxyphenyl)-8-(thiophen-3-yl)imidazo[1,2-a]pyrazin-3(7H)-one (3g, TMD-336)

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thiophen-3-yl)pyrazin-2-amine (7g) (311 mg, 811 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (396 mg, 1.22 mmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (780 μL) at 0° C., and the mixture was heated to reflux for 15 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3g (TMD-336) (179 mg, 431 μmol, 53.2%) as an orange solid. R_(f)=0.70 (ethyl acetate); HPLC retention time 7.9 min; ¹H NMR (400 MHz, CD₃OD) δ 4.18 (s, 2H), 6.70-6.76 (AA′BB′, 2H), 6.91-6.99 (AA′BB′, 2H), 7.11-7.19 (AA′BB′, 2H), 7.70 (dd, 1H, J=2.8, 5.2 Hz), 7.81-7.88 (AA′BB′, 2H), 7.95 (dd, 1H, J=1.2, 5.2 Hz), 8.29 (s, 1H), 8.50 (dd, 1H, J=1.2, 2.8 Hz); IR (KBr, cm⁻¹) 519, 652, 804, 841, 926, 1173, 1233, 1271, 1341, 1437, 1508, 1609, 1647, 3107; HRMS (ESI⁺) m/z 416.1065 ([M+H]⁺, C₂₃H₁₈N₃O₃S⁺ requires 416.1063).

1-7) TMD-281 (3h)

3-(Benzo[b]thiophen-2-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7h)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (971 mg, 2.55 mmol) in toluene (27 mL) and ethanol (1.3 mL) were successively added benzo[b]thiophene-2-boronic acid (6h) (500 mg, 2.81 mmol), dichlorobis(triphenylphosphine)palladium (II) (108 mg, 153 μmol) and 1 M Na₂CO₃ aqueous solution (2.60 mL, 2.60 mmol) at room temperature and the mixture was heated to reflux for 17 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7h (746 mg, 1.72 mmol, 67.3%) as an orange solid. R_(f)=0.67 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.20 (s, 6H), 0.95 (s, 9H), 6.68 (s, 2H), 6.91-6.98 (AA′BB′, 2H), 7.33-7.41 (m, 2H), 7.81-7.88 (m, 1H), 7.91-7.99 (m, 3H, includes AA′BB′), 8.11 (s, 1H), 8.55 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.2 (2C), 122.0, 122.3, 124.37, 124.42, 125.1, 126.5 (2C), 129.8, 131.0, 137.8, 139.4, 139.6, 140.9, 143.1, 150.4, 155.3; IR (KBr, cm⁻¹) 527, 552, 584, 642, 675, 708, 723, 741, 779, 808, 835, 918, 974, 1009, 1072, 1101, 1128, 1165, 1221, 1252, 1371, 1418, 1462, 1510, 1533, 1566, 1605, 1636, 1728, 2857, 2895, 2928, 2955, 3161, 3294, 3416; HRMS (ESI⁺) m/z 434.1713 ([M+H]⁺, C₂₄H₂₈N₃OSSi⁺ requires 434.1717).

8-(Benzo[b]thiophen-2-yl)-2-(4-hydroxybenzyl)-6-(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one (3h, TMD-281)

Under an argon atmosphere, to a mixture of 3-(benzo[b]thiophen-2-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7h) (153 mg, 352 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (190 mg, 539 μmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (400 μL) at 0° C. and the mixture was heated to reflux for 14 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3h (TMD-281) (31.0 mg, 66.6 μmol, 18.9%) as an orange solid. R_(f)=0.67 (ethyl acetate/methanol=20/1); HPLC retention time 19.9 min; ¹H NMR (400 MHz, CD₃OD) δ 4.12 (s, 2H), 6.75-6.84 (AA′BB′, 2H), 6.84-6.94 (AA′BB′, 2H), 7.16-7.24 (AA′BB′, 2H), 7.32-7.45 (m, 2H), 7.77-7.84 (m, 2H), 7.85-7.92 (AA′BB′, 2H), 8.30 (s, 1H), 8.35 (s, 1H); IR (KBr, cm⁻¹) 430, 523, 573, 621, 637, 658, 725, 746, 839, 885, 962, 1107, 1173, 1204, 1233, 1342, 1441, 1519, 1560, 1611, 1655, 3057.

1-8) TMD-337 (3i)

3-(Benzo[b]thiophen-3-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7i)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.50 g, 3.94 mmol) in toluene (45 mL) and ethanol (1.8 mL) were successively added thianaphthene-3-boronic acid (6i) (842 mg, 4.73 mmol), dichlorobis(triphenylphosphine)palladium (II) (165 mg, 235 μmol) and 1 M Na₂CO₃ aqueous solution (4.00 mL, 4.00 mmol) at room temperature, and the mixture was heated to reflux for 15 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 150 g, n-hexane/ethyl acetate=3/1) to give Compound 7i (1.19 g, 3.11 mmol, 78.9%) as an orange solid. R_(f)=0.30 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.21 (s, 6H), 0.96 (s, 9H), 6.29 (s, 2H), 6.89-6.95 (AA′BB′, 2H), 7.41-7.92 (m, 2H), 7.85-7.92 (AA′BB′, 2H), 7.95-8.02 (m, 1H), 8.07-8.13 (m, 1H), 8.16 (s, 1H), 8.55 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 120.1 (2C), 122.8, 123.6, 124.4, 124.6, 126.3 (2C), 127.7, 130.4, 132.2, 133.7, 137.3, 138.0, 139.3, 139.7, 152.5, 155.0; IR (KBr, cm⁻¹) 471, 631, 664, 683, 712, 733, 758, 781, 808, 839, 912, 968, 1011, 1059, 1080, 1103, 1128, 1169, 1188, 1263, 1346, 1362, 1389, 1447, 1508, 1605, 2857, 2886, 2928, 2953, 3065, 3177, 3298, 3368, 3472; HRMS (ESI⁺) m/z 434.1725 ([M+H]⁺, C₂₄H₂₈N₃OSSi⁺ requires 434.1769).

8-(Benzo[b]thiophen-3-yl)-2-(4-hydroxybenzyl)-6-(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one (3i, TMD-337)

Under an argon atmosphere, to a mixture of 3-(benzo[b]thiophen-3-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7i) (336 mg, 775 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (378 mg, 1.16 mmol) in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (780 μL) at 0° C. and the mixture was heated to reflux for 18 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3i (TMD-337) (136 mg, 292 μmol, 37.6%) as an orange solid. R_(f)=0.37 (ethyl acetate); HPLC retention time 11.5 min; ¹H NMR (400 MHz, CD₃OD) δ 4.16 (s, 2H), 6.68-6.77 (AA′BB′, 2H), 6.90-6.96 (AA′BB′, 2H), 7.07-7.15 (AA′BB′, 2H), 7.43-7.54 (m, 2H), 7.90-7.97 (AA′BB′, 2H), 8.00-8.07 (m, 1H), 8.22-8.30 (m, 1H), 8.36 (s, 1H), 8.52 (s, 1H); IR (KBr, cm⁻¹) 517, 571, 637, 735, 764, 839, 959, 1049, 1107, 1171, 1231, 1354, 1362, 1437, 1508, 1608, 3101; HRMS (ESI⁺) m/z 466.1233 ([M+H]⁺, C₂₇H₂₀N₃O₃S⁺ requires 466.1220).

1-9) TMD-280 (3j)

3,5-Bis[4-(text-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7j) (known compound, Reference: P. Jeanjot, et al., Synthesis, 513-522 (2003))

Under an argon atmosphere, to a solution of 3,5-dibromopyrazin-2-amine (42) (1.00 g, 3.95 mmol) dissolved in toluene (60 mL) and ethanol (4.0 mL) were successively added (4-bromophenoxy)(tert-butyl)dimethylsilane (6j) (2.49 g, 9.89 mmol), dichlorobis(triphenylphosphine)palladium (II) (167 mg, 237 μmol) and 1 M Na₂CO₃ aqueous solution (8.00 mL, 8.00 mmol) at room temperature, and the mixture was heated to reflux for 17 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=4/1) to give Compound 7j (1.75 g, 3.45 mmol, 87.4%) as a yellow solid. R_(f)=0.26 (n-hexane/ethyl acetate=4/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.18 (s, 6H), 0.22 (s, 6H), 0.93 (s, 9H), 0.96 (s, 9H), 6.11 (s, 2H), 6.85-6.91 (AA′BB′, 2H), 6.91-6.97 (AA′BB′, 2H), 7.65-7.71 (AA′BB′, 2H), 7.81-7.87 (AA′BB′, 2H), 8.40 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.5 (4C), 18.0 (2C), 25.6 (6C), 119.9 (2C), 120.1 (2C), 126.4 (2C), 129.6 (2C), 130.6, 130.8, 136.6, 137.7, 139.8, 151.5, 154.9, 155.5; IR (KBr, cm⁻¹) 438, 513, 573, 633, 665, 675, 696, 739, 781, 806, 824, 841, 912, 1009, 1086, 1103, 1167, 1202, 1263, 1362, 1379, 1408, 1422, 1452, 1512, 1566, 1605, 2857, 2885, 2928, 2955, 3061, 3183, 3304, 3377, 3478; HRMS (ESI⁺) m/z 508.2820 ([M+H]⁺, C₂₈H₄₂N₃O₂Si₂ ⁺ requires 508.2810).

2-(4-Hydroxybenzyl)-6,8-bis(4-hydroxyphenyl)imidazo[1,2-a]pyrazin-3(7H)-one (3j, TMD-280)

Under an argon atmosphere, to a mixture of 3,5-bis[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7j) (366 mg, 721 μmol) and 3-[4-(tert-butyldimethylsilyloxy)phenyl]-1,1-diethoxypropan-2-one (8) (380 mg, 1.08 mmol) dissolved in 1,4-dioxane (2 mL) was added 4 M hydrochloric acid (900 μL) at 0° C., and the mixture was heated to reflux for 16 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure, and the residue was purified by column chromatography in an argon flow (acidic silica gel 20 g, n-hexane/ethyl acetate=1/2→ethyl acetate→ethyl acetate/methanol=20/1). To the suspension obtained during the concentration under reduced pressure was added n-hexane. The precipitates were collected by filtration and dried in vacuo to give Compound 3j (TMD-280) (96.4 mg, 227 μmol, 31.4%) as an orange solid. R_(f)=0.22 (ethyl acetate); HPLC retention time 5.2 min; ¹H NMR (400 MHz, CD₃OD) δ 4.12 (s, 2H), 6.65-6.71 (AA′BB′, 2H), 6.88-6.94 (AA′BB′, 2H), 6.94-7.02 (AA′BB′, 2H), 7.06-7.12 (AA′BB′, 2H), 7.74-7.84 (AA′BB′, 2H), 7.91-7.98 (AA′BB′, 2H), 8.24 (s, 1H); IR (KBr, cm⁻¹) 554, 841, 891, 1132, 1242, 1273, 1341, 1437, 1458, 1508, 1543, 1558, 1609, 1653, 2812, 2895, 3096; HRMS (ESI⁺) m/z 426.1458 ([M+H]⁺, C₂₅H₂₀N₃O₄ ⁺ requires 426.1448).

Synthesis Example 2

Coelenteramide (CTMD) analogues modified at the C-3 position

2-1) TMD-344 (4a)

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-{5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-phenylpyrazin-2-yl}acetamide (11a)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.07 g, 4.02 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (680 μL, 8.04 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-phenylpyrazin-2-amine (7a) (504 mg, 1.33 mmol) and 4-(dimethylamino)pyridine (16.3 mg, 133 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 18 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=4/1) to give Compound 11a (630 mg, 1.01 mmol, 75.4%) as a yellow foamy solid. R_(f)=0.33 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.18 (s, 6H), 0.23 (s, 6H), 0.94 (s, 9H), 0.96 (s, 9H), 3.47 (s, 2H), 6.72-6.79 (AA′BB′, 2H), 6.96-7.02 (AA′BB′, 2H), 7.03-7.09 (AA′BB′, 2H), 7.29-7.39 (m, 3H), 7.66-7.74 (m, 2H), 8.05-8.12 (AA′BB′, 2H), 8.98 (s, 1H), 10.54 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.9, 18.0, 25.50 (3C), 25.54 (3C), 41.7, 119.5 (2C), 120.3 (2C), 127.8 (2C), 127.9, 128.0 (2C), 128.2 (2C), 128.5, 128.9, 130.3 (2C), 130.5, 137.6, 142.8, 147.6, 148.0, 153.8, 156.7, 169.3; IR (KBr, cm⁻¹) 523, 694, 781, 804, 839, 914, 1020, 1070, 1086, 1105, 1169, 1263, 1371, 1416, 1510, 1605, 1672, 2857, 2886, 2930, 2955, 3040, 3059, 3233; HRMS (ESI⁺)/z 648.3043 ([M+Na]⁺, C₃₆H₄₇N₃NaO₃Si₂ ⁺ requires 648.3048).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-phenylpyrazin-2-yl]acetamide (4a, TMD-344)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-phen ylpyrazin-2-yl]acetamide (11a) (500 mg, 799 μmol) in THF (7 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (4.00 mL, 4.00 mmol) at 0° C., and the mixture was stirred for 40 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with saturated NH₄Cl aqueous solution (200 mL), water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4a (TMD-344) (206 mg, 517 μmol, 64.7%) as a colorless solid. R_(f)=0.41 (dichloromethane/methanol=9/1); HPLC retention time 6.5 min; ¹H NMR (400 MHz, CD₃OD) δ 3.51 (s, 2H), 6.69-6.76 (AA′BB′, 2H), 6.87-6.94 (AA′BB′, 2H), 7.02-7.08 (AA′BB′, 2H), 7.30-7.43 (m, 3H), 7.58-7.65 (m, 2H), 7.96-8.02 (AA′BB′, 2H), 8.80 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.8, 115.2 (2C), 116.0 (2C), 125.3, 126.5, 128.0 (2C), 128.2 (2C), 128.3 (2C), 128.7, 130.4 (2C), 137.4, 137.7, 142.5, 147.8, 148.7, 156.2, 159.3, 169.9; IR (KBr, cm⁻¹) 527, 607, 675, 700, 799, 841, 968, 1020, 1165, 1225, 1265, 1323, 1368, 1410, 1443, 1458, 1493, 1518, 1537, 1593, 1609, 1676, 3021, 3256, 3368; HRMS (ESI⁺) m/z 420.1321 ([M+Na]⁺, C₂₄H₁₉N₃NaO₃ ⁺ requires 420.1319).

2-2) TMD-343 (4b)

(E)-2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-styrylpyrazin-2-yl]acetamide (11b)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.65 g, 6.19 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.05 mL, 12.4 mmol) at 0° C. and the mixture was stirred for 40 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of (E)-5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-styrylpyrazin-2-amine (7b) (500 mg, 1.24 mmol) and 4-(dimethylamino)pyridine (15.3 mg, 125 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 15 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11b (563 mg, 864 μmol, 69.7%) as a yellow solid. R_(f)=0.29 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.24 (s, 6H), 0.96 (s, 9H), 0.97 (s, 9H), 3.66 (s, 2H), 6.81-6.91 (m, 3H, includes AA′BB′), 6.99-7.04 (AA′BB′, 2H), 7.28-7.40 (m, 7H, includes AA′BB′), 7.82 (d, 1H, J=16 Hz), 8.11-8.19 (AA′BB′, 2H), 8.91 (s, 1H), 10.66 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.5 (2C), −4.6 (2C), 17.8, 17.9, 25.5 (6C), 42.0, 119.7 (2C), 120.3 (2C), 122.5, 127.1 (2C), 128.2 (2C), 128.5, 128.7 (2C), 128.9, 129.0, 130.3 (2C), 133.8, 136.0, 137.8, 142.8, 143.9, 148.0, 154.0, 156.7, 170.6; IR (KBr, cm⁻¹) 471, 521, 638, 691, 746, 781, 806, 839, 914, 968, 1007, 1080, 1103, 1169, 1263, 1325, 1371, 1391, 1414, 1439, 1472, 1510, 1566, 1605, 1659, 2857, 2886, 2930, 2055, 3028, 3057, 3217; HRMS (ESI⁺) m/z 674.3203 ([M+Na]⁺, C₂₈H₄₉N₃NaO₃Si₂ ⁺ requires 674.3205).

(E)-2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-styrylpyrazin-2-yl]acetamide (4b, TMD-343)

To a solution of (E)-2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-styrylpyrazin-2-yl]acetamide (11b) (500 mg, 767 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (3.90 mL, 3.90 mmol) at 0° C., and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4b (TMD-343) (251 mg, 592 μmol, 77.3%) as a yellow solid. R_(f)=0.50 (dichloromethane/methanol=9/1); HPLC retention time 10.6 min; NMR (400 MHz, CD₃OD) δ 3.67 (s, 2H), 6.79-6.90 (m, 3H, includes AA′BB′), 6.90-6.96 (AA′BB′, 2H), 7.25-7.32 (m, 3H, includes AA′BB′), 7.33-7.39 (m, 4H), 7.88 (d, 1H, J=16 Hz), 8.00-8.07 (AA′BB′, 2H), 8.72 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 42.2, 115.5 (2C), 116.0 (2C), 122.5, 126.2, 126.6, 127.3 (2C), 128.4 (2C), 128.8, 128.9 (2C), 130.2 (2C), 133.9, 136.1, 137.7, 142.5, 144.1, 148.7, 156.5, 159.3, 171.1; IR (KBr, cm⁻¹) 527, 617, 691, 756, 804, 845, 970, 1134, 1175, 1246, 1269, 1327, 1375, 1449, 1497, 1512, 1593, 1609, 1638, 3024, 3159, 3566; HRMS (ESI⁺) m/z 446.1475 ([M+Na]⁺, C₂₆H₂₁N₃NaO₃ ⁺ requires 446.1475).

2-3) TMD-347 (4c)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(1-phenylvinyl)pyrazin-2-amine (7c)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.00 g, 2.63 mmol) in toluene (30 mL) and ethanol (1.2 mL) were successively added 1-phenylvinylboronic acid (6c) (467 mg, 3.16 mmol), dichlorobis(triphenylphosphine)palladium (II) (110 mg, 157 μmol) and 1 M Na₂CO₃ aqueous solution (2.70 mL, 2.70 mmol) at room temperature, and the mixture was heated to reflux for 15 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7c (830 mg, 2.06 mmol, 78.2%) as a brown oily substance. R_(f)=0.33 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.15 (s, 6H), 0.91 (s, 9H), 5.50 (s, 1H), 5.93 (s, 2H), 5.97 (s, 1H), 6.80-6.87 (AA′BB′, 2H), 7.26-7.36 (m, 5H), 7.71-7.77 (AA′BB′, 2H), 8.45 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (2C), 17.9, 25.5 (3C), 117.9, 120.0 (2C), 126.3 (2C), 126.5 (2C), 128.0, 128.4 (2C), 130.5, 137.7, 138.2, 139.0, 139.2, 144.4, 151.8, 154.9; IR (KBr, cm⁻¹) 517, 552, 608, 629, 677, 692, 708, 779, 806, 843, 910, 1009, 1026, 1063, 1105, 1148, 1169, 1202, 1263, 1323, 1362, 1389, 1423, 1449, 1510, 1605, 2857, 2886, 2928, 2953, 3034, 3055, 3175, 3298, 3387, 3481.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-{5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(1-phenylvinyl)pyrazin-2-yl}acetamide (11c)

Under an argon atmosphere, to a mixture of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.80 g, 6.76 mmol) in CH₂Cl₂ (15 mL) was added DMF (4 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.20 mL, 14.2 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(1-phenylvinyl)pyrazin-2-amine (7c) (543 mg, 1.35 mmol) and 4-(dimethylamino)pyridine (15.0 mg, 123 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C., and the mixture was heated with stirring at 50° C. for 16 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11c (292 mg, 448 μmol, 33.3%) as a yellow foamy solid. R_(f)=0.26 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.13 (s, 6H), 0.18 (s, 6H), 0.91 (s, 9H), 0.92 (s, 9H), 3.22 (s, 2H), 5.51 (s, 1H), 5.65 (s, 1H), 6.67-6.74 (AA′BB′, 2H), 6.90-6.97 (AA′BB′, 2H), 6.97-7.03 (AA′BB′, 2H), 7.19-7.26 (m, 2H), 7.26-7.31 (m, 3H), 7.91-7.98 (AA′BB′, 2H), 8.95 (s, 1H), 10.19 (s, 1H); ¹³C NMR (75.5 MHz, acetone-d₆) δ −4.3 (4C), 18.6, 18.7, 26.0 (6C), 42.5, 118.8, 120.5 (2C), 121.1 (2C), 127.9 (2C), 128.4, 128.6, 128.78 (2C), 128.84 (2C), 130.1, 131,3 (2C), 138.4, 140.0, 144.2, 146.9, 148.7, 148.9, 155.1, 157.9, 169.7; IR (KBr, cm⁻¹) 546, 696, 781, 806, 839, 914, 1007, 1082, 1169, 1261, 1362, 1420, 1435, 1472, 1508, 1605, 1670, 2857, 2886, 2930, 2955, 3030, 3055, 3231; HRMS (ESI⁺) m/z 652.3390 ([M+H]⁺, C₃₈H₅₀N₃O₃Si₂ ⁺ requires 652.3385).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(1-phenylvinyl)pyrazin-2-yl]acetamide (4c, TMD-347)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(1-phenylvinyl)pyrazin-2-yl]acetamide (11c) (240 mg, 368 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.90 mL, 1.90 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4c (TMD-347) (83.9 mg, 198 μmol, 53.8%) as a brown solid. R_(f)=0.37 (dichloromethane/methanol=9/1); HPLC retention time 8.0 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.15 (s, 2H), 5.52 (s, 1H), 5.66 (s, 1H), 6.58-6.64 (AA′BB′, 2H), 6.80-6.86 (AA′BB′, 2H), 6.86-6.93 (AA′BB′, 2H), 7.19-7.25 (m, 2H), 7.25-7.31 (m, 3H), 7.84-7.91 (AA′BB′, 2H), 8.89 (s, 1H), 9.20 (s, 1H), 9.83 (s, 1H), 10.54 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.1, 115.0 (2C), 115.9 (2C), 118.1, 125.4, 126.5, 127.1 (2C), 127.7, 128.15 (2C), 128.20 (2C), 130.3 (2C), 137.8, 139.0, 143.1, 145.5, 148.1, 148.7, 156.1, 159.2, 169.6; IR (KBr, cm⁻¹) 519, 546, 606, 698, 779, 837, 916, 1107, 1171, 1231, 1321, 1431, 1481, 1514, 1609, 1670, 3026, 3265; HRMS (ESI⁺) m/z 446.1483 ([M+Na]⁺, C₂₆H₂₁N₃NaO₃ ⁺ requires 446.1475).

2-4) TMD-338 (4d)

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(naphthalen-1-yl)pyrazin-2-yl]acetamide (11d)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.00 mL, 11.8 mmol) at 0° C. and the mixture was stirred for 40 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(naphthalen-1-yl)pyrazin-2-amine (7d) (500 mg, 1.17 mmol) and 4-(dimethylamino)pyridine (15.3 mg, 125 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) at. 0° C. and the mixture was heated with stirring at 50° C. for 16 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11d (442 mg, 653 μmol, 55.9%) as a yellow foamy solid. R_(f)=0.26 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.13 (s, 6H), 0.19 (s, 6H), 0.91 (s, 9H), 0.92 (s, 9H), 3.24 (s, 2H), 6.54-6.60 (AA′BB′, 2H), 6.65-6.72 (AA′BB′, 2H), 6.91-6.98 (AA′BB′, 2H), 7.36-7.54 (m, 4H), 7.61-7.69 (m, 1H), 7.87-8.08 (m, 4H, includes AA′BB′), 9.09 (s, 1H), 10.27 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.90, 17.94, 25.48 (3C), 25.55 (3C), 119.4 (2C), 120.4 (2C), 125.0, 125.4, 125.7, 126.2, 126.8, 128.0, 128.15, 128.21 (2C), 128.6, 128.9 (2C), 129.9, 130.7, 133.4, 134.8, 138.2, 144.4, 147.9, 148.3, 153.5, 156.7, 169.3 (one carbon at the benzyl position was unobservable due to overlapping with the septet peak of DMSO); IR (KBr, cm⁻¹) 492, 538, 675, 718, 779, 806, 839, 914, 1007, 1080, 1115, 1169, 1260, 1362, 1420, 1441, 1472, 1510, 1605, 1670, 2857, 2886, 2930, 2955, 3046, 3223; HRMS (ESI⁺) m/z 698.3205 ([M+Na]⁺, C₄₀H₄₉N₃NaO₃Si₂ ⁺ requires 698.3205).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(naphthalen-1-yl)pyrazin-2-yl]acetamide (4d, TMD-338)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(naphthalen-1-yl)pyrazin-2-yl]acetamide (11d) (291 mg, 430 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (2.20 mL, 2.20 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with saturated NH₄Cl aqueous solution (200 mL), water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4d (TMD-338) (181 mg, 404 μmol, 93.8%) as a brown solid. R_(f)=0.56 (dichloromethane/methanol=9/1); HPLC retention time 9.1 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.17 (s, 2H), 6.45-6.53 (AA′BB′, 2H), 6.56-6.64 (AA′BB′, 2H), 6.80-6.88 (AA′BB′, 2H), 7.35-7.56 (m, 4H), 7.61-7.68 (m, 1H), 7.88-8.04 (m, 4H, includes AA′BB′), 9.03 (s, 1H), 9.15 (s, 1H), 9.85 (s, 1H), 10.14 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.2, 115.0 (2C), 115.9 (2C), 125.1, 125.3, 125.4, 125.8, 126.3, 126.5, 126.9, 128.25, 128.27 (2C), 128.7, 129.8 (2C), 130.7, 133.4, 134.9, 138.0, 144.0, 148.38, 148.44, 155.9, 159.2, 169.8; IR (KBr, cm⁻¹) 492, 540, 623, 777, 802, 839, 982, 1078, 1171, 1231, 1317, 1364, 1447, 1477, 1516, 1609, 1670, 3055, 3246; HRMS (ESI⁺) m/z 470.1483 ([M+Na]⁺, C₂₈H₂₁N₃NaO₃ ⁺ requires 470.1475).

2-5) TMD-339 (4e)

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(naphthalen-2-yl)pyrazin-2-yl]acetamide (11e)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.00 mL, 11.8 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(naphthalen-2-yl)pyrazin-2-amine (7e) (500 mg, 1.17 mmol) and 4-(dimethylamino)pyridine (15.0 mg, 123 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C., and the mixture was heated with stirring at 50° C. for 16 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11e (460 mg, 681 μmol, 58.2%) as a yellow foamy solid. R_(f)=0.26 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.12 (s, 6H), 0.21 (s, 6H), 0.91 (s, 9H), 0.94 (s, 9H), 3.46 (s, 2H), 6.55-6.65 (AA′BB′, 2H), 6.91-6.97 (AA′BB′, 2H), 6.97-7.03 (AA′BB′, 2H), 7.47-7.58 (m, 2H), 7.75-8.00 (m, 4H), 8.08-8.14 (AA′BB′, 2H), 8.23 (s, 1H), 9.00 (s, 1H), 10.63 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.8, 17.9, 25.5 (6C), 119.4 (2C), 120.3 (2C), 125.5, 126.1, 126.6, 127.1, 127.2, 127.3, 127.5, 127.9, 128.2 (2C), 128.5, 130.2 (2C), 132.6, 132.8, 135.3, 137.6, 143.0, 147.5, 148.0, 153.7, 156.7, 169.4 (one carbon at the benzyl position was unobservable due to overlapping with the septet peak of DMSO); IR (KBr, cm⁻¹) 478, 527, 687, 718, 746, 781, 804, 839, 914, 1009, 1082, 1103, 1128, 1169, 1261, 1362, 1415, 1445, 1472, 1508, 1605, 1670, 2857, 2886, 2928, 2955, 3057, 3221; HRMS (ESI⁺) m/z 698.3194 ([M+Na]⁺, C₄₀H₄₉N₃NaO₃Si₂ ⁺ requires 698.3205).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(naphthalen-2-yl)pyrazin-2-yl]acetamide (4e, TMD-339)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}]-3-(naphthalen-2-yl)pyrazin-2-yl]acetamide (11e) (300 mg, 444 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (2.30 mL, 2.30 mmol) at 0° C., and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with saturated NH₄Cl aqueous solution (200 mL), water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4e (TMD-339) (131 mg, 292 μmol, 65.8%) as a brown solid. R_(f)=0.48 (dichloromethane/methanol=9/1); HPLC retention time 10.9 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.39 (s, 2H), 6.50-6.58 (AA′BB′, 2H), 6.82-6.94 (2AA′BB′, 4H), 7.46-7.58 (m, 2H), 7.79-7.91 (m, 4H), 8.02-8.08 (AA′BB′, 2H), 8.23 (s, 1H), 8.94 (s, 1H), 9.20 (s, 1H), 9.88 (s, 1H), 10.52 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.6, 115.1 (2C), 115.9 (2C), 125.3, 125.6, 126.3, 126.5, 126.8, 127.3, 127.5, 127.6, 128.3 (2C), 128.6, 130.2 (2C), 132.7, 132.9, 135.3, 137.3, 142.7, 147.5, 148.6, 156.1, 159.3, 169.8; IR (KBr, cm⁻¹) 529, 635, 669, 752, 826, 968, 1163, 1223, 1356, 1454, 1491, 1516, 1539, 1593, 1611, 1672, 3065, 3246; HRMS (ESI⁺) m/z 470.1486 ([M+Na]⁺, C₂₈H₂₁N₃NaO₃ ⁺ requires 470.1475).

2-6) TMD-340 (4f)

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(thio phen-2-yl)pyrazin-2-yl]acetamide (11f)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (2.12 g, 7.96 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.35 mL, 16.0 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thiophen-2-yl)pyrazin-2-amine (7f) (600 mg, 1.59 mmol) and 4-(dimethylamino)pyridine (19.8 mg, 162 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 15 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1). The resulting solid was recrystallized (n-hexane/ethyl acetate) to give Compound 11f (446 mg, 706 μmol, 44.4%) as a colorless solid. R_(f)=0.26 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.18 (s, 6H), 0.23 (s, 6H), 0.94 (s, 9H), 0.97 (s, 9H), 3.65 (s, 2H), 0.678-6.86 (AA′BB′, 2H), 6.97-7.06 (m, 3H, includes AA′BB′), 7.19-7.27 (AA′BB′, 2H), 7.51 (dd, 1H, J=0.9, 3.7 Hz), 7.69 (dd, 1H, J=0.9, 5.0 Hz), 8.06-8.14 (AA′BB′, 2H), 8.93 (s, 1H), 10.60 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.9, 18.0, 25.50 (3C), 25.54 (3C), 41.9, 119.6 (2C), 120.4 (2C), 127.8, 127.9, 128.0, 128.2 (2C), 128.4, 129.5, 130.5 (2C), 137.3, 140.5, 140.6, 142.5, 148.0, 153.9, 157.0, 170.3; IR (KBr, cm⁻¹) 419, 519, 673, 704, 741, 781, 802, 839, 916, 1169, 1265, 1335, 1362, 1373, 1414, 1439, 1472, 1510, 1605, 1667, 2857, 2887, 2930, 2955, 3221; HRMS (ESI) m/z 654.2617 ([M+Na]⁺, C₃₄H₄₅N₃NaO₃Si₂ ⁺ requires 654.2612).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(thiophen-2-yl)pyrazin-2-yl]acetamide (4f, TMD-340)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(thio phen-2-yl)pyrazin-2-yl]acetamide (11f) (252 mg, 398 μmol) in THF (4 mL) added tetrabutylammonium fluoride (1.0 M THF solution) (2.00 mL, 2.00 mmol) at 0° C., and the mixture was stirred for an hour while elevating to room temperature, To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with saturated NH₄Cl aqueous solution (200 mL), water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. Filtration and concentration under reduced pressure gave Compound 4f (TMD-340) (160 mg, 397 μmol, 99.6%) as a colorless solid. R_(f)=0.37 (dichloromethane/methanol=9/1); HPLC retention time 6.8 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.59 (s, 2H), 6.70-6.76 (AA′BB′, 2H), 6.90-6.96 (AA′BB′, 2H), 6.99 (dd, 1H, J=3.8, 5.0 Hz), 7.12-7.18 (AA′BB′, 2H), 7.48 (dd, 1H, J=1.1, 3.8 Hz), 7.69 (dd, 1H, J=1.1, 5.0 Hz), 8.01-8.07 (AA′BB′, 2H), 8.89 (s, 1H), 9.32 (s, 1H), 9.97 (s, 1H), 10.50 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 42.0, 115.2 (2C), 116.0 (2C), 125.2, 126.0, 128.1, 128.25, 128.34 (2C), 129.6, 130.5 (2C), 137.1, 140.1, 140.8, 142.7, 148.6, 156.3, 159.5, 170.8; IR (KBr, cm⁻¹) 523, 631, 698, 725, 791, 841, 966, 984, 1074, 1113, 1167, 1227, 1263, 1317, 1375, 1406, 1431, 1450, 1495, 1518, 1535, 1593, 1609, 1674, 3021, 3244, 3372; HRMS (ESI⁺) m/z 426.0877 ([M+Na]⁺, C₂₂H₁₇N₃NaO₃S⁺ requires 426.0883).

2-7) TMD-345 (4g)

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-{5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thiophen-3-yl)pyrazin-2-yl}acetamide (11g)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.00 mL, 11.8 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thiophen-3-yl)pyrazin-2-amine (7g) (450 mg, 1.17 mmol) and 4-(dimethylamino)pyridine (15.5 mg, 127 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 15 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11g (512 mg, 809 μmol, 69.0%) as a yellow solid. R_(f)=0.22 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.16 (s, 6H), 0.20 (s, 6H), 0.92 (s, 9H), 0.94 (s, 9H), 3.56 (s, 2H), 6.72-6.82 (AA′BB′, 2H), 6.93-7.02 (AA′BB′, 2H), 7.12-7.22 (AA′BB′, 2H), 7.50 (dd, 1H, J=2.9, 5.0 Hz), 7.59 (d, 1H, J=5.0 Hz), 7.81 (d, 1H, J=2.9 Hz), 8.04-8.12 (AA′BB′, 2H), 8.91 (s, 1H), 10.50 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.90, 17.95, 25.50 (3C), 25.54 (3C), 41.9, 119.6 (2C), 120.3 (2C), 125.7, 126.0, 127.7, 127.9, 128.2 (2C), 128.8, 130.5 (2C), 137.1, 138.2, 142.0, 143.5, 148.0, 153.9, 156.8, 169.9; IR (KBr, cm⁻¹) 517, 669, 712, 741, 781, 806, 839, 914, 1007, 1082, 1105, 1169, 1261, 1341, 1362, 1441, 1472, 1508, 1605, 1665, 2857, 2886, 2930, 2955, 3057, 3227; HRMS (ESI⁺) m/z 654.2618 ([M+Na]⁺, C₃₄H₄₅N₃NaO₃Si₂ ⁺ requires 654.2612).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(thiophen-3-yl)pyrazin-2-yl]acetamide (4g, TMD-345)

To a solution of 2-[4-(tert-butyldimethyl silyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(thio phen-3-yl)pyrazin-2-yl]acetamide (11g) (310 mg, 491 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (2.50 mL, 2.50 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4g (TMD-345) (85.0 mg, 211 μmol, 43.0%) as a yellow solid. R_(f)=0.50 (dichloromethane/methanol=9/1); HPLC retention time 6.2 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.50 (s, 2H), 6.65-6.72 (AA′BB′, 2H), 6.84-6.92 (AA′BB′, 2H), 7.03-7.11 (AA′BB′, 2H), 7.49 (dd, 1H, J=2.9, 5.0 Hz), 7.58 (dd, 1H, J=1.2, 5.0 Hz), 7.80 (dd, 1H, J=1.2, 2.9 Hz), 7.98-8.06 (AA′BB′, 2H), 8.85 (s, 1H), 9.27 (s, 1H), 9.87 (s, 1H), 10.39 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.9, 115.2 (2C), 115.9 (2C), 125.2, 125.9, 126.2, 126.4, 127.8, 128.3 (2C), 130.4 (2C), 136.9, 138.3, 141.6, 143.7, 148.6, 156.3, 159.3, 170.4; IR (KBr, cm⁻¹) 419, 517, 609, 671, 706, 783, 804, 839, 934, 1040, 1082, 1111, 1173, 1227, 1248, 1272, 1312, 1352, 1441, 1516, 1593, 1611, 1674, 2808, 3250; HRMS (ESI⁺) m/z 426.0878 ([M+Na]⁺, C₂₂H₁₇N₃NaO₃S⁺ requires 426.0883).

2-8) TMD-342 (4h)

N-[3-(Benzo[b]thiophen-2-yl)-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11h)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (985 μL, 11.6 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 3-(benzo[b]thiophen-2-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7h) (505 mg, 1.16 mmol) and 4-(dimethylamino)pyridine (15.0 mg, 123 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyl dimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 15 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1). The resulting solid was recrystallized (n-hexane/ethanol) to give Compound 11h (294 mg, 431 μmol, 37.0%) as a colorless solid. R_(f)=0.19 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.19 (s, 6H), 0.25 (s, 6H), 0.96 (s, 9H), 0.97 (s, 9H), 3.71 (s, 2H), 6.82-6.89 (AA′BB′, 2H), 7.01-7.08 (AA′BB′, 2H), 7.26-7.42 (m, 4H, includes AA′BB′), 7.60-7.65 (m, 2H), 7.96 (d, 1H, J=7.9 Hz), 8.10-8.18 (AA′BB′, 2H), 9.02 (s, 1H), 10.82 (s, 1H); IR (KBr, cm⁻¹) 525, 677, 692, 710, 727, 743, 779, 797, 808, 835, 922, 972, 1011, 1074, 1171, 1256, 1327, 1362, 1391, 1416, 1445, 1503, 1603, 1657, 859, 2886, 2930, 2957, 3059, 3161, 3211; HRMS (ESI⁺) m/z 704.2758 ([M+Na]⁺, C₃₈H₄₇N₃NaO₃SSi₂ ⁺ requires 704.2769).

N-[3-(Benzo[b]thiophen-2-yl)-5-(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)acetamide (4h, TMD-342)

To a solution of N-[3-(benzo[b]thiophen-2-yl)-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11h) (186 mg, 273 μmol) in THF (2 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.40 mL, 1.40 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with saturated NH₄Cl aqueous solution (200 mL), water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. Filtration and concentration under reduced pressure gave Compound 4h (TMD-342) (123 mg, 271 μmol, 99.3%) as a colorless solid. R_(f)=0.41 (dichloromethane/methanol=9/1); HPLC retention time 13.1 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.62 (s, 2H), 6.70-6.78 (AA′BB′, 2H), 6.89-6.95 (AA′BB′, 2H), 7.17-7.22 (AA′BB′, 2H), 7.30-7.39 (m, 2H), 7.51-7.59 (m, 2H), 7.90-7.95 (m, 1H), 8.01-8.09 (AA′BB′, 2H), 8.94 (s, 1H), 9.38 (s, 1H), 9.96 (s, 1H), 10.70 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 42.3, 115.4 (2C), 116.1 (2C), 122.3, 124.3, 124.60, 124.63, 125.1, 125.6, 125.8, 128.4 (2C), 130.5 (2C), 137.8, 139.9, 140.3, 141.0, 141.5, 142.0, 148.5, 156.5, 159.6, 170.6; IR (KBr, cm⁻¹) 525, 554, 579, 623, 654, 681, 727, 804, 827, 847, 972, 1013, 1070, 1128, 1175, 1242, 1314, 1377, 1439, 1497, 1514, 1593, 1676, 3302; HRMS (ESI⁺) m/z 476.1052 ([M+Na]⁺, C₂₆H₁₉N₃NaO₃S⁺ requires 476.1039).

2-9) TMD-346 (4i)

N-[3-(Benzo[b]thiophen-3-yl)-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11i)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.00 mL, 11.8 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 3-(benzo[b]thiophen-3-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7i) (505 mg, 1.16 mmol) and 4-(dimethylamino)pyridine (15.0 mg, 123 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyl dimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 15 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11i (505 mg, 740 μmol, 63.5%) as a yellow solid. R_(f)=0.19 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.15 (s, 6H), 0.20 (s, 6H), 0.91 (s, 9H), 0.93 (s, 9H), 3.41 (s, 2H), 6.65-6.71 (AA′BB′, 2H), 6.93-7.00 (2AA′BB′, 4H), 7.35-7.42 (m, 2H), 7.80 (s, 1H), 7.95-8.07 (m, 4H, includes AA′BB′), 9.01 (s, 1H), 10.49 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.5 (4C), 17.89, 17.93, 25.47 (3C), 25.54 (3C), 41.6, 119.5 (2C), 120.4 (2C), 122.6, 123.5, 124.4 (2C), 127.3, 127.9, 128.1 (2C), 128.9, 130.3 (2C), 132.3, 137.5, 137.5, 139.4, 143.7, 143.8, 147.6, 153.8, 156.7, 169.4; IR (KBr, cm⁻¹) 683, 700, 735, 758, 781, 804, 839, 914, 1169, 1261, 1331, 1362, 1435, 1472, 1508, 1605, 1670, 2857, 2886, 2930, 2955; HRMS (ESI⁺) m/z 704.2781 ([M+Na]⁺, C₃₈H₄₇N₃NaO₃SSi₂ ⁺ requires 704.2769).

N-[3-(Benzo[b]thiophen-3-yl)-5-(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)acetamide (4i, TMD-346)

To a solution of N-[3-(benzo[b]thiophen-3-yl)-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11i) (300 mg, 440 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (2.20 mL, 2.20 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), and dried over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4i (TMD-346) (191 mg, 422 μmol, 95.8%) as a brown solid. R_(f)=0.50 (dichloromethane/methanol=9/1); HPLC retention time 9.6 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.36 (s, 2H), 6.57-6.63 (AA′BB′, 2H), 6.84-6.92 (2AA′BB′, 4H), 7.36-7.43 (m, 2H), 7.79 (s, 1H), 7.95-8.04 (m, 4H, includes AA′BB′), 8.95 (s, 1H), 9.22 (s, 1H), 9.88 (s, 1H), 10.37 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.7, 115.1 (2C), 116.0 (2C), 122.8, 123.6, 124.5 (2C), 125.2, 126.5, 127.5, 128.2 (2C), 130.2 (2C), 132.4, 137.2, 137.6, 139.5, 143.3, 144.0, 148.2, 156.1, 159.3, 169.9; IR (KBr, cm⁻¹) 419, 473, 525, 611, 735, 760, 837, 970, 1171, 1233, 1329, 1435, 1479, 1514, 1609, 1668, 2957, 3260; HRMS (ESI⁺) m/z 476.1052 ([M+Na]⁺, C₂₆H₁₉N₃O₃S⁺ requires 476.1039).

2-101 TMD-341 (4j)

N-[3,5-Bis{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11j)

Under an argon atmosphere, to a mixture of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (985 μL, 11.6 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 3,5-bis[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7j) (591 mg, 1.16 mmol) and 4-(dimethylamino)pyridine (15.7 mg, 129 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 15 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=4/1) to give Compound 11j (714 mg, 945 μmol, 81.1%) as a yellow foamy solid. R_(f)=0.37 (n-hexane/diethyl ether=2/3); ¹H NMR (400 MHz, DMSO-d₆) δ 0.14 (s, 6H), 0.19 (s, 6H), 0.20 (s, 6H), 0.92 (s, 9H), 0.95 (s, 18H), 3.47 (s, 2H), 6.71-6.78 (2AA′BB′, 4H), 6.94-7.02 (AA′BB′, 2H), 7.03-7.13 (AA′BB′, 2H), 7.57-7.63 (AA′BB′, 2H), 8.03-8.10 (AA′BB′, 2H), 8.91 (s, 1H), 10.49 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.5 (6C), 17.9 (3C), 25.5 (9C), 41.7, 119.3 (2C), 119.5 (2C), 120.3 (2C), 127.9, 128.1 (2C), 128.9, 129.3 (2C), 130.4 (2C), 130.7, 136.9, 142.4, 147.2, 147.8, 153.8, 155.7, 156.7, 169.3; IR (KBr, cm⁻¹) 523, 637, 677, 710, 781, 804, 839, 914, 1009, 1078, 1105, 1169, 1258, 1362, 1402, 1416, 1441, 1472, 1510, 1605, 1667, 2857, 2886, 2928, 2955, 3036, 3221; HRMS (ESI⁺) m/z 778.3853 ([M+Na]⁺, C₄₂H₆₁N₃NaO₄Si₃ ⁺ requires 778.3862).

N-[3,5-Bis(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)acetamide (4j, TMD-341)

To a solution of N-[3,5-bis{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11j) (500 mg, 661 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (5.00 mL, 5.00 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4j (TMD-341) (263 mg, 637 μmol, 96.3%) as a brown solid. R_(f)=0.43 (dichloromethane/methanol=9/1); HPLC retention time 4.3 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.40 (s, 2H), 6.60-6.68 (AA′BB′, 2H), 6.68-6.74 (AA′BB′, 2H), 6.82-6.90 (AA′BB′, 2H), 6.94-7.03 (AA′BB′, 2H), 7.54-7.62 (AA′BB′, 2H), 7.94-8.02 (AA′BB′, 2H), 8.80 (s, 1H), 9.24 (s, 1H), 9.70 (s, 1H), 9.85 (s, 1H), 10.29 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.7, 115.1 (4C), 115.9 (2C), 125.4, 126.6, 128.1, 128.2 (2C), 129.6 (2C), 130.3 (2C), 136.3, 141.9, 147.8, 148.4, 156.1, 158.3, 159.2, 170.0; IR (KBr, cm⁻¹) 530, 571, 839, 966, 1011, 1080, 1171, 1234, 1321, 1369, 1420, 1481, 1516, 1609, 1670, 3246; HRMS (ESI⁺) m/z 436.1269 ([M+Na]⁺, C₂₄H₁₉N₃NaO₄ ⁺ requires 436.1268).

2-11) TMD-373 (4k)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(thieno[3,2-b]thiophen-2-yl)pyrazin-2-amine (7k)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (500 mg, 1.31 mmol) in toluene (15 mL) and ethanol (600 μL) were successively added thieno[3,2-b]thiophen-2-boronic acid (6k) (290 mg, 1.58 mmol), dichlorobis(triphenylphosphine)palladium (II) (56.0 mg, 79.8 μmol) and 1 M Na₂CO₃ aqueous solution (1.40 mL, 1.40 mmol) at room temperature and the mixture was heated to reflux for 21 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 7k (278 mg, 632 μmol, 48.0%) as an orange solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.19 (s, 6H), 0.94 (s, 9H), 6.55 (s, 2H), 6.89-6.96 (AA′BB′, 2H), 7.44 (d, 1H, J=5.3 Hz), 7.71 (d, 1H, J=5.3 Hz), 7.86-7.94 (AA′BB′, 2H), 8.08 (s, 1H), 8.49 (s, 1H); IR (KBr, cm⁻¹) 509, 637, 702, 781, 839, 916, 986, 1103, 1165, 1261, 1344, 1418, 1464, 1510, 1605, 1638, 2857, 2930, 2953, 3156, 3296, 3416.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(thieno[3,2-b]thiophen-2-yl)pyrazin-2-yl]acetamide (11k)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (757 mg, 2.84 mmol) in CH₂Cl₂ (8 mL) was added DMF (2 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (490 μL, 5.79 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thieno[3,2-b]thiophen-2-yl)pyrazin-2-amine (7k) (250 mg, 569 μmol and 4-(dimethylamino)pyridine (12.3 mg, 101 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 13 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 30 g, n-hexane/ethyl acetate=3/1) to give Compound 11k (228 mg, 331 μmol, 58.2%) as a yellow solid. R_(f)=0.26 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.22 (s, 6H), 0.93 (s, 9H), 0.95 (s, 9H), 3.67 (s, 2H), 6.78-6.86 (AA′BB′, 2H), 6.96-7.04 (AA′BB′, 2H), 7.20-7.30 (AA′BB′, 2H), 7.41 (d, 1H, J=5.2 Hz), 7.57 (s, 1H), 7.73 (d, 1H, J=5.2 Hz), 8.04-8.13 (AA′BB′, 2H), 8.92 (s, 1H), 10.69 (s, 1H); IR (KBr, cm⁻¹) 527, 635, 702, 779, 837, 918, 1007, 1074, 1169, 1256, 1362, 1445, 1508, 1603, 1655, 2857, 2886, 2928, 2955, 3211.

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(thieno[3,2-b]thiophen-2-yl)pyrazin-2-yl]acetamide (4k, TMD-373)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(thieno[3,2-b]thiophen-2-yl)pyrazin-2-yl]acetamide (11k) (172 mg, 250 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.30 mL, 1.30 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4k (TMD-373) (88.4 mg, 192 μmol, 77.1%) as a yellow solid. R_(f)=0.37 (dichloromethane/methanol=9/1); HPLC retention time 10.6 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.59 (s, 2H), 6.71-6.78 (AA′BB′, 2H), 6.85-6.94 (AA′BB′, 2H), 7.15-7.23 (AA′BB′, 2H), 7.37-7.42 (m, 2H), 7.72 (d, 1H, J=5.2 Hz), 7.99-8.05 (AA′BB′, 2H), 8.87 (s, 1H), 9.38 (s, 1H), 9.95 (s, 1H), 10.61 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 42.3, 115.4 (2C), 115.9 (2C), 120.1, 120.5, 125.0, 125.8, 128.3 (2C), 130.4 (2C), 130.5, 137.1, 139.7, 140.0, 141.0, 142.4, 142.9, 148.4, 156.5, 159.5, 170.5; IR (KBr, cm⁻¹) 530, 635, 704, 725, 804, 986, 1173, 1242, 1325, 1371, 1439, 1491, 1514, 1609, 1676, 3304.

2-12) TMD-374 (4l)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(dithieno[3,2-b:2′,3′-d]thiophen-2-yl)pyrazin-2-amine (7l)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (700 mg, 1.84 mmol) in toluene (21 mL) and ethanol (840 μL) were successively added dithieno[3,2-b:2′,3′-d]thiophen-2-boronic acid (6l) (540 mg, 2.25 mmol), dichlorobis(triphenylphosphine)palladium (II) (78.2 mg, 111 μmol) and 1 M Na₂CO₃ aqueous solution (1.90 mL, 1.90 mmol) at room temperature, and the mixture was heated to reflux for 18 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7l (477 mg, 963 μmol, 52.3%) as a yellow solid. R_(f)=0.26 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.20 (s, 6H), 0.94 (s, 9H), 6.59 (s, 2H), 6.89-6.97 (AA′BB′, 2H), 7.53 (d, 1H, J=5.2 Hz), 7.74 (d, 1H, J=5.2 Hz), 7.88-7.97 (AA′BB′, 2H), 8.16 (s, 1H), 8.51 (s, 1H); IR (KBr, cm⁻¹) 530, 625, 644, 698, 781, 839, 908, 1072, 1109, 1179, 1225, 1267, 1360, 1393, 1462, 1512, 1605, 2857, 2928, 2957, 3173, 3285, 3424.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(dithieno[3,2-b:2′,3′-d]thiophen-2-yl)pyrazin-2-yl]acetamide (11l)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.00 g, 3.76 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (640 μL, 7.56 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(thieno[3,2-b:2′,3′-d]thiophen-2-yl)pyrazin-2-amine (7l) (370 mg, 746 μmol) and 4-(dimethylamino)pyridine (14.8 mg, 121 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1). The resulting solid was recrystallized (n-hexane/ethyl acetate) to give Compound 11l (116 mg, 156 μmol, 20.9%) as a brown solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.16 (s, 6H), 0.21 (s, 6H), 0.93 (s, 9H), 0.94 (s, 9H), 3.68 (s, 2H), 6.78-6.88 (AA′BB′, 2H), 6.94-7.06 (AA′BB′, 2H), 7.20-7.30 (AA′BB′, 2H), 7.47 (d, 1H, J=5.2 Hz), 7.65 (s, 1H), 7.75 (d, 1H, J=5.2 Hz), 8.06-8.14 (AA′BB′, 2H), 8.93 (s, 1H), 10.72 (s, 1H); IR (KBr, cm⁻¹) 530, 602, 644, 700, 779, 837, 922, 1072, 1171, 1265, 1361, 1447, 1504, 1603, 1657, 2857, 2928, 2955, 3208.

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(thieno[3,2-b:2′,3′-d]thiophen-2-yl)pyrazin-2-yl]acetamide (4l, TMD-374)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(dithieno[3,2-b:2′,3′-d]thiophen-2-yl)pyrazin-2-yl]acetamide (11l) (82.3 mg, 111 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (600 μL, 600 μmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4l (TMD-374) (50.7 mg, 192 μmol, 88.8%) as a yellow solid. R_(f)=0.37 (dichloromethane/methanol=9/1); HPLC retention time 17.7 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.61 (s, 2H), 6.70-6.80 (AA′BB′, 2H), 6.87-6.94 (AA′BB′, 2H), 7.15-7.25 (AA′BB′, 2H), 7.44 (s, 1H), 7.52 (d, 1H, J=5.2 Hz), 7.75 (d, 1H, J=5.2 Hz), 8.01-8.09 (AA′BB′, 2H), 8.89 (s, 1H), 9.34 (s, 1H), 9.96 (s, 1H), 10.66 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 42.3, 115.4 (2C), 115.9 (2C), 121.4, 121.9, 125.0, 125.7, 128.3 (2C), 128.9, 130.3, 130.4 (2C), 132.3, 137.2, 140.0, 141.8, 142.00, 142.02, 142.8, 148.4, 156.5, 159.5, 170.5; IR (KBr, cm⁻¹) 534, 598, 644, 706, 793, 835, 893, 972, 1109, 1173, 1190, 1242, 1319, 1389, 1439, 1491, 1611, 1665, 3231.

2-13) TMD-375 (4m)

3-(2,2′-Bithiophen-5-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7m)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (500 mg, 1.31 mmol) in toluene (15 mL) and ethanol (600 μL) were successively added 5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene (6m) (460 mg, 1.57 mmol), dichlorobis(triphenylphosphine)palladium (II) (56.3 mg, 80.2 μmol) and 1 M Na₂CO₃ aqueous solution (1.40 mL, 1.40 mmol) at room temperature, followed by heating to reflux for 15 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 7m (574 mg, 1.23 mmol, 93.7%) as a yellow solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.19 (s, 6H), 0.94 (s, 9H), 6.49 (s, 2H), 6.88-6.97 (AA′BB′, 2H), 7.10 (dd, 1H, J=3.7, 3.7 Hz), 7.34 (d, 1H, J=3.7 Hz), 7.41 (d, 1H, J=3.7 Hz), 7.53 (d, 1H, J=4.0 Hz), 7.70 (d, 1H, J=4.0 Hz), 7.84-7.92 (AA′BB′, 2H), 8.47 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), 18.0, 25.5 (3C), 120.2 (2C), 124.5, 124.9, 125.9, 126.5 (2C), 126.6, 128.5, 129.8, 131.2, 136.4, 137.1, 138.1, 139.5, 141.6, 149.8, 155.3; IR (KBr, cm⁻¹) 505, 544, 694, 781, 806, 839, 914, 980, 1011, 1084, 1169, 1209, 1258, 1375, 1418, 1454, 1512, 1605, 2857, 2928, 2953, 3177, 3296, 3453.

N-[3-(2,2′-Bithiophen-5-yl)-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11m)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.00 g, 3.76 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (640 μL, 7.56 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 3-(2,2′-bithiophen-5-yl)-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7m) (350 mg, 752 μmol) and 4-(dimethylamino)pyridine (15.0 mg, 123 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyl dimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11m (298 mg, crude) as a brown oily substance. R_(f)=0.26 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.16 (s, 6H), 0.22 (s, 6H), 0.92 (s, 9H), 0.94 (s, 9H), 3.64 (s, 2H), 6.76-6.85 (AA′BB′, 2H), 6.98-7.05 (AA′BB′, 2H), 7.06-7.13 (m, 2H), 7.19-7.27 (AA′BB′, 2H), 7.33 (d, 1H, J=3.6 Hz), 7.36 (d, 1H, J=3.6 Hz), 7.54-7.59 (m, 1H), 8.05-8.11 (AA′BB′, 2H), 8.91 (s, 1H), 10.65 (s, 1H).

N-[3-(2,2′-Bithiophen-5-yl)-5-(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)acetamide (4m, TMD-375)

To a solution of N-[3-(2,2′-bithiophen-5-yl)-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11m) (168 mg, crude) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.20 mL, 1.20 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4m (TMD-375) (102 mg, 210 μmol, 49.5% (2 steps)) as a yellow solid. R_(f)=0.44 (dichloromethane/methanol=9/1); HPLC retention time 15.3 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.57 (s, 2H), 6.66-6.75 (AA′BB′, 2H), 6.85-6.95 (AA′BB′, 2H), 7.06-7.17 (m, 4H, includes AA′BB′), 7.34-7.40 (m, 2H), 7.53-7.58 (m, 1H), 7.98-8.05 (AA′BB′, 2H), 8.85 (s, 1H), 9.30 (s, 1H), 9.95 (s, 1H), 10.53 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 42.0, 115.2 (2C), 115.9 (2C), 124.6, 124.9, 125.1, 125.8, 126.3, 128.3 (2C), 128.6, 129.0, 130.4 (2C), 136.1, 137.1, 139.4, 139.5, 140.1, 142.1, 148.5, 156.3, 159.5, 170.7; IR (KBr, cm⁻¹) 532, 602, 692, 837, 966, 1105, 1165, 1223, 1265, 1369, 1450, 1491, 1516, 1609, 1676, 3246, 3385.

2-14) TMD-376 (4n)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-[4-(dimethylamino)phenyl]pyrazin-2-amine (7n)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (500 mg, 1.31 mmol) in toluene (15 mL) and ethanol (600 μL) were successively added 4-(dimethylamino)phenylboronic acid (6n) (260 mg, 1.58 mmol), dichlorobis(triphenylphosphine)palladium (II) (56.1 mg, 79.9 μmol) and 1 M Na₂CO₃ aqueous solution (1.40 mL, 1.40 mmol) at room temperature, followed by heating to reflux for 24 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=2/1) to give Compound 7n (488 mg, 1.16 mmol, 88.3%) as a yellow solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.92 (s, 9H), 2.94 (s, 6H), 6.02 (s, 2H), 6.75-6.83 (AA′BB′, 2H), 6.83-6.92 (AA′BB′, 2H), 7.60-7.70 (AA′BB′, 2H), 7.77-7.88 (AA′BB′, 2H), 8.32 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), 17.9, 25.5 (3C), 39.9 (2C), 111.9 (2C), 120.0 (2C), 125.0, 126.3 (2C), 128.9 (2C), 130.7, 135.5, 138.5, 139.7, 150.4, 151.3, 154.8; IR (KBr, cm⁻¹) 432, 511, 633, 698, 808, 824, 912, 1009, 1063, 1103, 1167, 1254, 1360, 1422, 1454, 1510, 1607, 2803, 2857, 2886, 2928, 2953, 3179, 3300, 3476.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-{4-(dimethylamino)phenyl}pyrazin-2-yl]acetamide (11n)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.00 g, 3.76 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (640 μL, 7.56 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-[4-(dimethylamino)phenyl]pyrazin-2-amine (7n) (315 mg, 749 μmol) and 4-(dimethylamino)pyridine (14.8 mg, 121 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyl dimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was hetated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=2/1) to give Compound 11n (200 mg, 300 μmol, 40.0%) as a yellow solid. R_(f)=0.26 (n-hexane/ethyl acetate=2/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.23 (s, 6H), 0.95 (s, 9H), 0.97 (s, 9H), 2.95 (s, 6H), 3.50 (s, 2H), 6.52-6.65 (AA′BB′, 2H), 6.75-6.85 (AA′BB′, 2H), 6.95-7.05 (AA′BB′, 2H), 7.10-7.20 (AA′BB′, 2H), 7.56-7.66 (AA′BB′, 2H), 8.04-8.10 (AA′BB′, 2H), 8.82 (s, 1H), 10.41 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), −4.6 (2C), 17.9, 18.0, 25.5 (6C), 39.8 (2C), 41.8, 111.3 (2C), 119.5 (2C), 120.3 (2C), 124.4, 128.05, 128.07 (2C), 128.9 (2C), 129.2, 130.4 (2C), 135.8, 142.0, 147.78, 147.84, 150.5, 153.8, 156.6, 169.3; IR (KBr, cm⁻¹) 527, 685, 781, 839, 914, 1080, 1167, 1256, 1371, 1441, 1508, 1607, 1668, 2857, 2928, 2955, 3233.

N-[3-{4-(Dimethylamino)phenyl}-5-(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)acetamide (4n, TMD-376)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-{4-(dimethylamino)phenyl}pyrazin-2-yl]acetamide (11n) (148 mg, 220 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.10 mL, 1.10 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4n (TMD-376) (85.3 mg, 194 μmol, 87.8%) as a yellow solid. R_(f)=0.37 (dichloromethane/methanol=9/1); HPLC retention time 4.5 min; ¹H NMR (400 MHz, DMSO-d₆) δ 2.91 (s, 6H), 3.41 (s, 2H), 6.51-6.59 (AA′BB′, 2H), 6.62-6.70 (AA′BB′, 2H), 6.82-6.90 (AA′BB′, 2H), 6.98-7.08 (AA′BB′, 2H), 7.53-7.62 (AA′BB′, 2H), 7.94-8.01 (AA′BB′, 2H), 8.74 (s, 1H), 9.25 (s, 1H), 9.83 (s, 1H), 10.28 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 39.8 (2C), 41.9, 111.4 (2C), 115.0 (2C), 115.8 (2C), 124.4, 125.3, 126.7, 128.1 (2C), 128.9 (2C), 130.3 (2C), 135.5, 141.6, 147.8, 148.3, 150.6, 156.2, 159.1, 169.8; IR (KBr, cm⁻¹) 538, 691, 816, 949, 1101, 1169, 1250, 1321, 1375, 1437, 1514, 1533, 1609, 1647, 2810, 3005, 3167, 3348.

2-15) TMD-377 (4o)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(4-nitrophenyl)pyrazin-2-amine (7o)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (500 mg, 1.31 mmol) in toluene (15 mL) and ethanol (600 μL) were successively added p-nitrophenylboronic acid (6o) (263 mg, 1.58 mmol), dichlorobis(triphenylphosphine)palladium (II) (56.1 mg, 79.9 μmol) and 1 M Na₂CO₃ aqueous solution (1.40 mL, 1.40 mmol) at room temperature, followed by heating to reflux for 22 hours. After cooling to room temperature, to the mixture was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 7o (451 mg, 1.07 mmol, 81.2%) as a yellow solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.92 (s, 9H), 6.48 (s, 2H), 6.85-6.92 (AA′BB′, 2H), 7.82-7.92 (AA′BB′, 2H), 8.02-8.10 (AA′BB′, 2H), 8.26-8.36 (AA′BB′, 2H), 8.55 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), 18.0, 25.6 (3C), 120.1 (2C), 123.8 (2C), 126.5 (2C), 129.5 (2C), 130.0, 134.8, 138.8, 140.1, 144.3, 146.9, 151.8, 155.2; IR (KBr, cm⁻¹) 476, 511, 635, 700, 727, 806, 839, 913, 1026, 1084, 1169, 1213, 1279, 1348, 1402, 1464, 1516, 1603, 1643, 2859, 2951, 3142, 3300, 3372.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(4-nitrophenyl)pyrazin-2-yl]acetamide (11o)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.00 g, 3.76 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (640 μL, 7.56 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(4-nitrophenyl)pyrazin-2-amine (7o) (317 mg, 751 μmol) and 4-(dimethylamino)pyridine (15.3 mg, 125 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyldimethylsilyl oxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=2/1) to give Compound 11o (242 mg, 361 μmol, 48.1%) as a yellow solid. R_(f)=0.30 (n-hexane/ethyl acetate=2/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.15 (s, 6H), 0.20 (s, 6H), 0.92 (s, 9H), 0.93 (s, 9H), 3.44 (s, 2H), 6.67-6.74 (AA′BB′, 2H), 6.94-7.07 (2AA′BB′, 4H), 7.80-7.86 (AA′BB′, 2H), 8.01-8.12 (2AA′BB′, 4H), 9.05 (s, 1H), 10.85 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), −4.6 (2C), 17.9, 18.0, 25.50 (3C), 25.51 (3C), 41.6, 119.4 (2C), 120.4 (2C), 123.2 (2C), 127.4, 128.2, 128.52 (2C), 128.54 (2C), 130.4 (2C), 138.7, 143.0, 144.5, 145.0, 146.9, 147.9, 153.9, 156.9, 168.9; IR (KBr, cm⁻¹) 700, 741, 781, 839, 914, 1169, 1265, 1348, 1443, 1508, 1603, 1670, 2857, 2930, 2955.

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(4-nitrophenyl)pyrazin-2-yl]acetamide (4o, TMD-377)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-(4-nitrophenyl)pyrazin-2-yl]acetamide (11o) (179 mg, 267 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.40 mL, 1.40 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4o (TMD-377) (98.0 mg, 222 μmol, 83.0%) as an orange solid. R_(f)=0.48 (dichloromethane/methanol=9/1); HPLC retention time 7.4 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.40 (s, 2H), 6.60-6.69 (AA′BB′, 2H), 6.86-6.93 (AA′BB′, 2H), 6.93-7.03 (AA′BB′, 2H), 7.81-7.89 (AA′BB′, 2H), 8.00-8.10 (2AA′BB′, 4H), 9.02 (s, 1H), 9.30 (s, 1H), 9.93 (s, 1H), 10.77 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 41.7, 115.0 (2C), 115.9 (2C), 123.2 (2C), 124.7, 126.1, 128.2 (2C), 128.6 (2C), 130.2 (2C), 138.4, 142.7, 144.5, 145.0, 146.9, 148.4, 156.3, 159.3, 169.2; IR (KBr, cm⁻¹) 534, 640, 696, 756, 799, 843, 1013, 1080, 1107, 1171, 1236, 1346, 1437, 1516, 1609, 1670, 3250.

2-16) TMD-378 (4p)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-(phenylethynyl)pyrazin-2-amine (7p)

Under an argon atmosphere, to a solution of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (1.50 g, 3.94 mmol) in diethylamine (20 mL) were successively added copper (I) iodide (450 mg, 2.36 mmol), phenylacetylene (6p) (900 μL, 8.19 mmol) and dichlorobis(triphenylphosphine)palladium (II) (139 mg, 198 μmol) at room temperature and the mixture was stirred for 4 hours. To this was added water and the metal catalyst was removed by filtration. The product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (300 mL) and brine (300 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 100 g, n-hexane/ethyl acetate=3/1) to give Compound 7p (1.56 g, 3.89 mmol, 98.6%) as a brown solid. R_(f)=0.52 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.17 (s, 6H), 0.92 (s, 9H), 6.75 (s, 2H), 6.85-6.92 (AA′BB′, 2H), 7.38-7.46 (m, 3H), 7.69-7.76 (m, 2H), 7.76-7.83 (AA′BB′, 2H), 8.50 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), 17.9, 25.5 (3C), 85.4, 94.2, 120.1 (2C), 121.6, 121.8, 126.5 (2C), 128.6 (2C), 129.3, 129.9, 131.9 (2C), 138.8, 140.0, 154.8, 155.2; IR (KBr, cm⁻¹) 529, 638, 689, 754, 781, 806, 824, 912, 1009, 1049, 1070, 1144, 1169, 1258, 1323, 1362, 1420, 1454, 1510, 1562, 1605, 2212, 2857, 2928, 2955, 3057, 3173, 3296, 3474.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(phenylethynyl)pyrazin-2-yl]acetamide (11p)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.00 g, 3.76 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (640 μL, 7.56 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(phenylethynyl)pyrazin-2-amine (7p) (300 mg, 747 μmol) and 4-(dimethylamino)pyridine (13.8 mg, 113 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyldimethylsilyl oxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11p (291 mg, 448 μmol, 60.0%) as a brown solid. R_(f)=0.19 (n-hexane/ethyl acetate=3/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.10 (s, 6H), 0.20 (s, 6H), 0.90 (s, 9H), 0.93 (s, 9H), 3.65 (s, 2H), 6.63-6.73 (AA′BB′, 2H), 6.92-7.02 (AA′BB′, 2H), 7.17-7.27 (AA′BB′, 2H), 7.33-7.48 (m, 5H), 7.96-8.05 (AA′BB′, 2H), 8.99 (s, 1H), 10.69 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.60 (2C), −4.61 (2C), 17.8, 17.9, 25.5 (6C), 41.7, 85.8, 94.5, 119.5 (2C), 120.4 (2C), 121.2, 128.2, 128.28 (2C), 128.34, 128.6 (2C), 129.5, 130.3 (2C), 131.8 (2C), 133.1, 138.5, 146.6, 148.0, 153.8, 156.9, 169.4; IR (KBr, cm⁻¹) 530, 689, 756, 781, 839, 914, 1007, 1125, 1169, 1258, 1379, 1433, 1510, 1605, 1672, 2214, 2857, 2930, 2955, 3235.

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-(phenylethynyl)pyrazin-2-yl]acetamide (4p, TMD-378)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-(phenylethynyl)pyrazin-2-yl]acetamide (11p) (198 mg, 305 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THE solution) (1.60 mL, 1.60 mmol) at 0° C., and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4p (TMD-378) (93.8 mg, 223 μmol, 73.1%) as a yellow solid. R_(f)=0.48 (dichloromethane/methanol=9/1); HPLC retention time 10.0 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.58 (s, 2H), 6.60-6.70 (AA′BB′, 2H), 6.83-6.93 (AA′BB′, 2H), 7.10-7.19 (AA′BB′, 2H), 7.24-7.33 (m, 3H), 7.33-7.49 (m, 2H), 7.91-7.98 (AA′BB′, 2H), 8.94 (s, 1H), 9.27 (s, 1H), 9.92 (s, 1H), 10.60 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 41.8, 86.0, 94.4, 115.2 (2C), 115.9 (2C), 121.2, 125.6, 125.9, 128.3 (2C), 128.7 (2C), 129.7, 130.3 (2C), 131.9 (2C), 133.2, 138.3, 146.3, 148.6, 156.2, 1159.4, 169.7; IR (KBr, cm⁻¹) 530, 615, 687, 758, 793, 839, 962, 1125, 1157, 1177, 1219, 1267, 1327, 1389, 1456, 1489, 1582, 1684, 2212, 3231, 3391.

2-17) Compound 4q

(Z)-5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-styrylpyrazin-2-amine (7q)

Under an argon atmosphere, to a solution of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(phenylethynyl)pyrazin-2-amine (7p) (100 mg, 249 μmol) in ethyl acetate (5 mL) was added Lindlar's catalyst (10% Pd) (40.0 mg) at room temperature. The atmosphere in the reaction flask was replaced with hydrogen gas and the mixture was stirred at room temperature for 30 hours. After replacing the atmosphere of the reaction system again with argon, to the mixture was added dichloromethane (15 mL) and stirred at room temperature for an hour. After removing the catalyst by filtration, the filtrate was washed successively with water (100 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 10 g, n-hexane/ethyl acetate=3/1) to give the mixture of Compounds 7q, 7p and 7r (98.2 mg) as a brown oil.

(Z)-2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-{5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-styrylpyrazin-2-yl}acetamide (11q)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (170 mg, 638 μmol) in CH₂Cl₂ (5 mL) was added DMF (1 drop) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (110 μL, 1.30 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to the mixture (50.3 mg) of 7q, 7p and 7r and 4-(dimethylamino)pyridine (3.0 mg, 25 μmol) dissolved in anhydrous pyridine (5 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (30 mL×3). The combined organic extract was washed successively with water (50 mL) and brine (100 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 10 g, n-hexane/ethyl acetate=3/1) to give the mixture (60.0 mg) of Compounds 11q, 11p and 11r as a yellow oily substance. R_(f)=0.20 (n-hexane/ethyl acetate=3/1).

Compound 4q can be prepared by deprotecting the TBDMS group from Compound 11q described above according to modifications of the process described in SYNTHESIS EXAMPLES of the other CTMD analogues.

2-18) TMD-379 (4r)

5-[4-(tert-Butyldimethylsilyloxy)phenyl]-3-phenethylpyrazin-2-amine (7r)

Under an argon atmosphere, to a solution of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-(phenylethynyl)pyrazin-2-amine (7p) (400 mg, 996 μmol) in ethyl acetate (20 mL) was added Palladium/charcoal activated (10% Pd) (80.0 mg) at room temperature. The atmosphere in the reaction flask was replaced with hydrogen gas and the mixture was stirred at room temperature for 3 hours. After replacing the atmosphere of the reaction system again with argon, to the mixture was added dichloromethane (15 mL) and stirred at room temperature for an hour. The catalyst was removed by filtration. After concentration under reduced pressure, the residue was purified by column chromatography (silica gel 40 g, n-hexane/ethyl acetate=2/1) to give Compound 7r (403 mg, 994 μmol, 99.8%) as a brown oily substance. R_(f)=0.48 (n-hexane/ethyl acetate=2/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.18 (s, 6H), 0.93 (s, 9H), 2.92 (t, 3H, J=8.0 Hz), 3.05 (t, 3H, J=8.0 Hz), 6.25 (s, 2H), 6.81-6.90 (AA′BB′, 2H), 7.10-7.18 (m, 1H), 7.18-7.35 (m, 4H), 7.75-7.85 (AA′BB′, 2H), 8.27 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), 18.0, 25.6 (3C), 31.7, 34.0, 120.0 (2C), 125.7, 126.1 (2C), 128.2 (2C), 128.5 (2C), 130.9, 135.6, 138.5, 140.1, 141.9, 152.3, 154.6; IR (KBr, cm⁻¹) 507, 635, 677, 698, 750, 781, 841, 914, 1009, 1103, 1146, 1167, 1213, 1254, 1389, 1420, 1454, 1512, 1605, 2857, 2928, 2955, 3061, 3318.

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-phenethylpyrazin-2-yl]acetamide (11r)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.40 g, 5.26 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (890 μL, 10.5 mmol) at 0° C. and the mixture was heated with stirring for 30 minutes while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-phenethylpyrazin-2-amine (7r) (403 mg, 994 μmol) and 4-(dimethylamino)pyridine (19.6 mg, 160 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=3/1) to give Compound 11r (298 mg, 455 μmol, 45.8%) as a yellow oily substance. R_(f)=0.44 (n-hexane/ethyl acetate=2/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.12 (s, 6H), 0.20 (s, 6H), 0.91 (s, 9H), 0.93 (s, 9H), 2.83 (t, 1H, J=8.4 Hz), 2.94 (t, 1H, J=8.4 Hz), 3.59 (s, 2H), 6.72-6.79 (AA′BB′, 2H), 6.92-7.00 (AA′BB′, 2H), 7.01-7.07 (AA′BB′, 2H), 7.07-7.15 (m, 1H), 7.16-7.24 (m, 4H), 7.97-8.05 (AA′BB′, 2H), 8.81 (s, 1H), 10.44 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ −4.5 (2C), −4.6 (2C), 17.9, 18.0, 25.5 (6C), 32.8, 34.7, 41.7, 119.6 (2C), 120.3 (2C), 125.7, 128.1 (2C), 128.2 (4C), 128.5, 129.1, 130.2 (2C), 130.3, 136.6, 141.4, 143.8, 147.9, 150.6, 153.8, 156.6, 170.3; IR (KBr, cm⁻¹) 525, 698, 781, 839, 914, 1007, 1169, 1258, 1362, 1416, 1443, 1510, 1605, 1661, 2857, 2930, 2955, 3225.

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)-3-phenethylpyrazin-2-yl]acetamide (4r, TMD-379)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}-3-phen ethylpyrazin-2-yl]acetamide (11r) (197 mg, 301 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (1.50 mL, 1.50 mmol) at 0° C. and the mixture was stirred for 30 minutes while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethyl acetate) to give Compound 4r (TMD-379) (100 mg, 236 μmol, 78.3%) as a yellow solid. R_(f)=0.44 (dichloromethane/methanol=9/1); HPLC retention time 9.5 min; ¹H NMR (400 MHz, DMSO-d₆) δ 2.81 (t, 1H, J=8.0 Hz), 2.92 (t, 1H, J=8.0 Hz), 3.52 (s, 2H), 6.62-6.72 (AA′BB′, 2H), 6.80-6.90 (AA′BB′, 2H), 6.98-7.05 (AA′BB′, 2H), 7.07-7.16 (m, 3H), 7.16-7.24 (m, 2H), 7.90-7.98 (AA′BB′, 2H), 8.76 (s, 1H), 9.27 (s, 1H), 9.83 (s, 1H), 10.35 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 33.0, 34.8, 41.7, 115.2 (2C), 115.8 (2C), 125.8, 126.6, 128.1 (2C), 128.26 (2C), 128.29 (2C), 128.6, 130.1 (2C), 136.4, 141.5, 143.4, 148.5, 150.7, 156.2, 159.0, 170.6; IR (KBr, cm⁻¹) 519, 606, 692, 839, 966, 1157, 1223, 1265, 1373, 1452, 1516, 1595, 1674, 3273.

2-19) TMD-348 (4s)

2-[4-(tert-Butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]acetamide (11s)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.00 mL, 11.8 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (7s) (350 mg, 1.16 mmol) and 4-(dimethylamino)pyridine (15.0 mg, 123 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=7/1) to give Compound 11s (478 mg, 869 μmol, 74.8%) as a yellow foamy solid. R_(f)=0.19 (n-hexane/ethyl acetate=6/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.14 (s, 6H), 0.19 (s, 6H), 0.91 (s, 9H), 0.94 (s, 9H), 3.66 (s, 2H), 6.75-6.82 (AA′BB′, 2H), 6.91-6.97 (AA′BB′, 2H), 7.17-7.24 (AA′BB′, 2H), 7.93-8.00 (AA′BB′, 2H), 8.90 (d, 1H, J=1.4 Hz), 9.28 (d, 1H, J=1.4 Hz), 10.99 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.8, 17.9, 25.46 (3C), 25.47 (3C), 41.8, 119.6 (2C), 120.2 (2C), 127.5 (2C), 128.2, 129.2, 130.4 (2C), 134.9, 138.7, 146.3, 147.0, 153.8, 156.2, 170.3; IR (KBr, cm⁻¹) 417, 517, 575, 638, 681, 708, 781, 806, 839, 914, 1009, 1051, 1103, 1167, 1260, 1354, 1416, 1468, 1508, 1545, 1605, 1670, 2857, 2886, 2930, 2955, 3034, 3063; HRMS (ESI⁺) m/z 550.2930 ([M+H]⁺, C₃₀H₄₄N₃O₃Si₂ ⁺ requires 550.2916).

2-(4-Hydroxyphenyl)-N-[5-(4-hydroxyphenyl)pyrazin-2-yl]acetamide (4s, TMD-348)

To a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]-N-[5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]acetamide (11s) (300 mg, 546 μmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (2.80 mL, 2.80 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4s (TMD-348) (191 mg, 422 μmol, 95.8%) as a brown solid. R_(f)=0.51 (dichloromethane/methanol=9/1); HPLC retention time 4.9 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.57 (s, 1H), 6.62-6.70 (AA′BB′, 2H), 6.79-6.84 (AA′BB′, 2H), 7.06-7.12 (AA′BB′, 2H), 7.83-7.92 (AA′BB′, 2H), 8.82 (d, 1H, J=1.4 Hz), 9.22 (d, 1H, J=1.4 Hz), 9.23 (s, 1H), 9.75 (s, 1H), 10.86 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.9, 115.2 (2C), 115.8 (2C), 125.7, 126.8, 127.7 (2C), 130.3 (2C), 134.9, 138.4, 146.7, 146.9, 156.3, 158.7, 170.7; IR (KBr, cm⁻¹) 419, 519, 613, 681, 804, 837, 910, 1020, 1051, 1107, 1171, 1252, 1356, 1443, 1508, 1541, 1611, 1676, 3026, 3354; HRMS (FAB⁺/glycerol) m/z 322.1187 ([M+H]⁺, C₁₈H₁₆N₃O₃ ⁺ requires 322.1192).

2-20) TMD-349 (4t)

N-[3-Bromo-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11t)

Under an argon atmosphere, to a solution of 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetic acid (9) (1.55 g, 5.82 mmol) in CH₂Cl₂ (10 mL) was added DMF (3 drops) by a Pasteur pipette at room temperature. To this was added oxalyl dichloride (1.00 mL, 11.8 mmol) at 0° C. and the mixture was stirred for an hour while elevating to room temperature. The mixture was concentrated under reduced pressure to give crude 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) as a colorless oil, which was used in the following reaction without further purification.

Under an argon atmosphere, to the mixture of 3-bromo-5-[4-(tert-butyldimethylsilyloxy)phenyl]pyrazin-2-amine (5) (443 mg, 1.16 mmol) and 4-(dimethylamino)pyridine (15.2 mg, 124 μmol) dissolved in anhydrous pyridine (20 mL) was added 2-[4-(tert-butyldimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was heated with stirring at 50° C. for 19 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (200 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=4/1) to give Compound 11t (431 mg, 685 μmol, 58.9%) as a yellow foamy solid. R_(f)=0.22 (n-hexane/diethyl ether=1/1); ¹H NMR (400 MHz, DMSO-d₆) δ 0.15 (s, 6H), 0.21 (s, 6H), 0.91 (s, 9H), 0.94 (s, 9H), 3.61 (s, 2H), 6.74-6.82 (AA′BB′, 2H), 6.94-7.01 (AA′BB′, 2H), 7.16-7.23 (AA′BB′, 2H), 7.94-8.01 (AA′BB′, 2H), 9.03 (s, 1H), 10.54 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ −4.6 (4C), 17.89, 17.93, 25.46 (3C), 25.52 (3C), 41.5, 119.6 (2C), 120.5 (2C), 127.3, 128.1, 128.4 (2C), 130.4 (2C), 136.3, 138.0, 144.6, 149.1, 153.8, 157.2, 169.8; IR (KBr, cm⁻¹) 467, 521, 623, 685, 716, 781, 802, 839, 914, 1007, 1047, 1078, 1107, 1169, 1256, 1333, 1362, 1412, 1441, 1474, 1508, 1566, 1605, 1672, 2857, 2886, 2930, 2955, 3032, 3057, 3231; HRMS (ESI⁺) m/z 650.1839 ([M+Na]⁺, C₃₀H₄₂BrN₃NaO₃Si₂ ⁺ requires 650.1840).

N-[3-Bromo-5-(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)acetamide (4t, TMD-349)

To a solution of N-[3-bromo-5-{4-(tert-butyldimethylsilyloxy)phenyl}pyrazin-2-yl]-2-[4-(tert-butyldimethylsilyloxy)phenyl]acetamide (11t) (290 mg, 461 μmmol) in THF (5 mL) was added tetrabutylammonium fluoride (1.0 M THF solution) (2.30 mL, 2.30 mmol) at 0° C., and the mixture was stirred for an hour while elevating to room temperature. To the mixture was added saturated NH₄Cl aqueous solution (50 mL) and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was recrystallized (n-hexane/ethanol) to give Compound 4t (TMD-349) (147 mg, 367 μmol, 79.5%) as a brown solid. R_(f)=0.50 (dichloromethane/methanol=9/1); HPLC retention time 5.5 min; ¹H NMR (400 MHz, DMSO-d₆) δ 3.54 (s, 2H), 6.65-6.71 (AA′BB′, 2H), 6.83-6.89 (AA′BB′, 2H), 7.08-7.14 (AA′BB′, 2H), 7.87-7.95 (AA′BB′, 2H), 8.97 (s, 1H), 9.25 (s, 1H), 10.00 (s, 1H), 10.45 (s, 1H); ¹³C NMR (75.5 MHz, DMSO-d₆) δ 41.5, 115.2 (2C), 116.0 (2C), 124.8, 125.4, 128.5 (2C), 130.3 (2C), 136.6, 137.7, 144.2, 149.8, 156.2, 159.8, 170.2; IR (KBr, cm⁻¹) 519, 623, 795, 839, 1047, 1080, 1173, 1229, 1271, 1339, 1449, 1483, 1516, 1609, 1676, 3275; HRMS (ESI⁺) m/z 422.0119 ([M+Na]⁺, C₁₈H₁₄BrN₃NaO₃ ⁺ requires 422.0111).

Synthesis Example 3

Coelenteramide (CTMD) analogues modified at the C-2 position

3-1) TMD-331 (4u)

1-[3-Benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-3-(4-methoxyphenyl)urea (11u)

Under an argon atmosphere, to a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int., 33, 477-485 (2001)) (306 mg, 1.05 mmol) in anhydrous 1,2-dichloroethane (10 mL) was added 4-methoxyphenyl isocyanate (13) (191 μL, 1.00 mmol) at room temperature, and the mixture was heated with stirring at 80° C. for 19 hours. After cooling to room temperature, the solid precipitated was collected by filtration and dried in vacuo to give the crude product (293 mg, <664 μmol, <63.2%) as a colorless solid. An aliquot (93.0 mg, <211 μmol) was recrystallized from methanol to give Compound 11u (54.9 mg, 125 μmol, 59.2%) as a colorless solid. R_(f)=0.50 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, DMSO-d₆) δ 3.73 (s, 3H), 3.81 (s, 3H), 4.36 (s, 2H), 6.98-6.93 (AA′BB′, 2H), 7.02-7.08 (AA′BB′, 2H), 7.17-7.25 (m, 1H), 7.28-7.32 (m, 4H), 7.43-7.48 (AA′BB′, 2H), 7.95-8.01 (AA′BB′, 2H), 8.79 (s, 1H), 9.04 (s, 1H), 10.58 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 38.5, 55.18, 55.24, 114.0 (2C), 114.4 (2C), 121.1 (2C), 126.3, 127.2 (2C), 128.2, 128.3 (2C), 129.0 (2C), 131.7, 134.5, 137.9, 144.4, 145.0, 145.4, 152.2, 155.1, 160.1; IR (KBr, cm⁻¹) 704, 746, 824, 1038, 1173, 1242, 1329, 1369, 1416, 1481, 1510, 1570, 1607, 1668, 2833, 3030, 3261; Anal. Calcd. For C₂₆H₂₄N₄O₃: C, 70.89; H, 5.49; N, 12.72. Found: C, 70.66; H, 5.49; N, 12.61.

1-[3-Benzyl-5-(4-hydroxyphenyl)pyrazin-2-yl]-3-(4-hydroxyphenyl)urea (4u, TMD-331)

Under an argon atmosphere, to a solution of 1-[3-benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-3-(4-methoxy phenyl)urea (11u) (200 mg, 454 μmol) in anhydrous dichloromethane (10 mL) was added boron tribromide (1.0 M dichloromethane solution, 2.27 mL, 2.27 mmol) at room temperature, and the mixture was heated to reflux for 24 hours. After cooling to room temperature, to this was added saturated aqueous sodium bicarbonate solution and the mixture was concentrated under reduced pressure using a rotary evaporator to remove dichloromethane. The solid was collected by filtration and dried in vacuo to give the crude product (180 mg) as a colorless solid. The solid was recrystallized from ethyl acetate/methanol to give Compound 4u (TMD-331) (98.2 mg, 238 μmol, 52.4%) as a colorless solid. R_(f)=0.66 (n-hexane/ethyl acetate=1/2); ¹H NMR (400 MHz, DMSO-d₆) δ 4.35 (s, 2H), 6.69-6.74 (AA′BB′, 2H), 6.84-6.88 (AA′BB′, 2H), 7.17-7.24 (m, 1H), 7.27-7.33 (m, 5H), 7.84-7.89 (AA′BB′, 2H), 8.72 (s, 1H), 8.95 (s, 1H), 9.19 (s, 1H), 9.79 (s, 1H), 10.49 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 38.5, 115.3 (2C), 115.7 (2C), 121.5 (2C), 126.3, 126.7, 127.4 (2C), 128.4 (2C), 128.9 (2C), 130.1, 134.2, 138.0, 144.8, 145.2, 152.3, 153.3, 158.5; IR (KBr, cm⁻¹) 519, 637, 702, 750, 835, 1105, 1171, 1223, 1246, 1369, 1445, 1481, 1508, 1578, 1609, 1681, 3035, 3256; Anal. Calcd. For C₂₄H₂₀N₄O₃: C, 69.89; H, 4.89; N, 13.58. Found: C, 69.58; H, 5.05; N, 13.37.

3-2) TMD-332 (4v)

1-[3-Benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-3-(4-methoxyphenyl)thiourea (11v)

Under an argon atmosphere, to a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int., 33, 477-485 (2001)) (291 mg, 1.00 mmol) in anhydrous DMF (5 mL) was added sodium hydride (43.6 mg, 1.00 mmol) at room temperature. To the mixture was added a solution of 4-methoxyphenyl isothiocyanate (14) (182 mg, 1.10 mmol) dissolved in anhydrous DMF (2 mL) at 0° C. and stirred for 5.5 hours at room temperature. To this was added aqueous 2 M HCl solution and the resulting solid was collected by filtration. The crude product was purified by column chromatography (silica gel 30 g, n-hexane/ethyl acetate/dichloromethane=57/3/40) to give the product as a yellow solid containing some impurities (327 mg, <716 μmol). The product was recrystallized from ethyl acetate to give Compound 11v (255 mg, 559 μmol, 55.9%) as a yellow solid. R_(f)=0.24 (n-hexane/ethyl acetate=4/1); ¹H NMR (400 MHz, DMSO-d₆) δ 3.75 (s, 3H), 3.82 (s, 3H), 4.42 (s, 2H), 6.90-6.96 (AA′BB′, 2H), 7.03-7.09 (AA′BB′, 2H), 7.20-7.26 (m, 1H), 7.30-7.36 (m, 4H), 7.38-7.45 (AA′BB′, 2H), 7.99-8.05 (AA′BB′, 2H), 8.83 (s, 1H), 9.65 (s, 1H), 11.76 (br s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 38.9, 55.2 (2C), 113.7 (2C), 114.4 (2C), 126.2 (2C), 126.5, 127.5 (2C), 128.0, 128.5 (2C), 129.0 (3C), 131.6, 134.7, 137.5, 144.9, 145.7, 157.1, 160.4, 179.0; IR (KBr, cm⁻¹) 581, 700, 741, 799, 833, 897, 1022, 1070, 1146, 1248, 1283, 1333, 2037, 2351, 2835, 2988, 3395; Anal. Calcd. For C₂₆H₂₄N₄O₂S: C, 68.40; H, 5.30; N, 12.27. Found: C, 68.47; H, 5.20; N, 12.26.

1-[3-Benzyl-5-(4-hydroxyphenyl)pyrazin-2-yl]-3-(4-hydroxyphenyl)thiourea (4v, TMD-332)

Under an argon atmosphere, to a solution of 1-[3-benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-3-(4-methoxy phenyl)thiourea (11v) (136 mg, 299 μmol) in anhydrous dichloromethane (7 mL) was added boron tribromide (1.0 M dichloromethane solution, 1.50 mL, 1.50 mmol) at room temperature, and the mixture was heated to reflux for 18 hours. After cooling to room temperature, to this was added saturated aqueous sodium bicarbonate solution and the mixture was concentrated under reduced pressure using a rotary evaporator to remove dichloromethane. The solid was collected by filtration and dried in vacuo to give the crude product (126 mg) as an orange solid. The solid was recrystallized from ethyl acetate to give Compound 4v (TMD-332) (80.6 mg, 188 μmol, 62.9%) as an orange solid. R_(f)=0.48 (n-hexane/ethyl acetate=1/2); ¹H NMR (400 MHz, DMSO-d₆) δ 4.40 (s, 2H), 6.70-6.76 (AA′BB′, 2H), 6.84-6.90 (AA′BB′, 2H), 7.20-7.35 (m, 7H), 7.88-7.94 (AA′BB′, 2H), 8.76 (s, 1H), 9.47 (s, 1H), 9.53 (s, 1H), 9.85 (s, 1H), 11.71 (br s, 1H); IR (KBr, cm⁻¹) 542, 584, 700, 741, 837, 1157, 1215, 1263, 1342, 1395, 1449, 1510, 1578, 1609, 2941, 3032, 3273, 3406; HRMS (ESI⁺) m/z 429.1382 ([M+H]⁺, C₂₄H₂₁N₄O₂S⁺ requires 429.1380).

3-3) TMD-330 (4w)

N-[3-Benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-2-(4-methoxyphenyl)propanamide (11w)

Under an argon atmosphere, 2-(4-methoxyphenyl)propanoic acid (synthesized by the process of I. Shiina, et al., Eur. J. Org. Chem., 5887-5890 (2008)) (1.20 g, 6.66 mmol) was dissolved in thionyl chloride (6.00 mL, 82.6 mmol) and the solution was heated to reflux for 27 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure to give the crude product of 2-(4-methoxyphenyl)propanoyl chloride (16) as a colorless oil. The product was used in the following reaction without further purification.

Under an argon atmosphere, to a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int, 33, 477-485 (2001)) (500 mg, 1.72 mmol) in pyridine (8 mL) were successively added 4-(dimethylamino)pyridine (21.0 mg, 172 μmol) and 2-(4-methoxyphenyl)propanoyl chloride (16) prepared above at room temperature, and the mixture was heated with stirring at 55° C. for 14 hours. After cooling to room temperature, to the mixture was added water and the product was extracted with dichloromethane (×3). The combined organic extract was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residual pyridine was azeotropically removed with toluene (×3). The residue was purified twice by column chromatography (silica gel 50 g, dichloromethane/ethyl acetate=9/1, and silica gel 50 g, n-hexane/ethyl acetate=9/1→6/1) to give Compound 11w (942 mg, <quant.) as a colorless foamy solid containing some impurities.

N-[3-Benzyl-5-(4-hydroxyphenyl)pyrazin-2-yl]-2-(4-hydroxyphenyl)propanamide (4w, TMD-330)

Under an argon atmosphere, to a solution of the crude product of N-[3-benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-2-(4-methoxyphenyl)propanamide (11w) (500 mg, <1.10 mmol) in anhydrous dichloromethane (20 mL) was added boron tribromide (1.0 M dichloromethane solution, 5.50 mL, 5.50 mmol) at room temperature, and the mixture was heated to reflux for 21 hours. After cooling to room temperature, to this was added saturated aqueous sodium bicarbonate solution and the mixture was concentrated under reduced pressure using a rotary evaporator to remove dichloromethane. The solid was collected by filtration and dried in vacuo to give the crude product (330 mg) as a brown solid. The solid was recrystallized from methanol to give Compound 4w (TMD-330) (112 mg, 263 μmol, <23.9% (2 steps)) as a colorless solid. R_(f)=0.26 (n-hexane/ethyl acetate=1/1); ¹H NMR (400 MHz, DMSO-d₆) δ 1.37 (d, 3H, J=7.0 Hz), 3.81 (q, 1H, J=7.0 Hz), 3.84-4.00 (m, 2H), 6.72-6.79 (AA′BB′, 2H), 6.85-6.96 (m, 4H), 7.09-7.19 (m, 3H), 7.21-7.27 (AA′BB′, 2H), 7.90-7.98 (AA′BB′, 2H), 8.79 (s, 1H), 9.31 (s, 1H), 9.87 (s, 1H), 10.30 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 18.3, 44.3, 115.2 (2C), 115.7 (2C), 126.1, 126.5, 128.0 (2C), 128.1 (2C), 128.4 (2C), 128.9 (2C), 131.6, 136.8, 138.3, 143.3, 148.6, 150.6, 156.3, 159.1, 173.4 (one carbon at the benzyl position was unobservable due to overlapping with the septet peak of DMSO); IR (KBr, cm⁻¹) 530, 596, 700, 725, 837, 924, 1171, 1225, 1267, 1319, 1375, 1450, 1487, 1545, 1611, 1670, 2976, 3310; HRMS (ESI⁺) m/z 448.1644 ([M+Na]⁺, C₂₆H₂₃N₃NaO₃ ⁺ requires 448.1632).

3-4) TMD-365 (4x)

N-[3-Benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-4-methoxybenzamide (11x)

To a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int., 33, 477-485 (2001)) (500 mg, 1.72 mmol) in pyridine (5 mL) were successively added 4-(dimethylamino)pyridine (21.0 mg, 172 μmol) and 4-methoxybenzoyl chloride (17) (587 mg, 3.44 mmol) at room temperature, and the mixture was heated with stirring at 50° C. for 17 hours. After cooling to room temperature, to the mixture was added water and the product was extracted with dichloromethane (×3). The combined organic extract was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residual pyridine was azeotropically removed with toluene (×3). The residue was purified by column chromatography (silica gel 50 g, dichloromethane/ethyl acetate=9/1). The residue was further recrystallized from ethyl acetate to give Compound 11x (592 mg, 1.39 mmol, 80.8%) as a colorless solid. R_(f)=0.63 (dichloromethane/ethyl acetate=9/1); ¹H NMR (400 MHz, DMSO-d₆) δ 3.83 (s, 3H), 3.85 (s, 3H), 4.17 (s, 2H), 7.04-7.11 (m, 4H), 7.14-7.26 (m, 5H), 7.93-7.98 (AA′BB′, 2H), 8.05-8.11 (AA′BB′, 2H), 8.96 (s, 1H), 10.63 (s, 1H); ¹³C NMR (67.8 MHz, DMSO+CDCl₃) δ 40.3, 54.7, 54.8, 112.9 (2C), 113.7 (2C), 125.4, 125.7, 127.4 (2C), 127.7 (2C), 128.0, 128.5 (2C), 129.4 (2C), 136.2, 137.6, 143.6, 148.2, 150.4, 160.1, 162.0, 165.5; IR (KBr, cm⁻¹) 700, 743, 843, 1030, 1159, 1177, 1258, 1290, 1452, 1485, 1514, 1535, 1580, 1609, 1643, 3242; Anal. Calcd. For C₂₆H₂₃N₃O₃: C, 73.39; H, 5.45; N, 9.88. Found: C, 73.48; H, 5.40; N, 9.94.

N-[3-Benzyl-5-(4-hydroxyphenyl)pyrazin-2-yl]-4-hydroxybenzamide (4x, TMD-365)

Under an argon atmosphere, to a solution of N-[3-benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-4-methoxybenzamide (11x) (300 mg, 705 μmol) in anhydrous dichloromethane (15 mL) was added boron tribromide (1.0 M dichloromethane solution, 3.53 mL, 3.53 mmol) at room temperature, and the mixture was was heated to reflux for 17 hours. After cooling to room temperature, to this was added saturated aqueous sodium bicarbonate solution and the mixture was concentrated under reduced pressure using a rotary evaporator to remove dichloromethane. The solid was collected by filtration and dried in vacuo to give the crude product (288 mg) as a brown solid. The solid was purified by column chromatography (silica gel 30 g, n-hexane/ethyl acetate=2/3). The product was further recrystallized from ethyl acetate to give Compound 4x (TMD-365) (119 mg, 300 μmol, 42.6%) as a yellow solid. R_(f)=0.46 (dichloromethane/methanol=9/1); ¹H NMR (400 MHz, DMSO-d₆) δ 4.14 (s, 2H), 6.83-6.92 (m, 4H), 7.12-7.27 (m, 5H), 7.81-7.88 (AA′BB′, 2H), 7.93-7.99 (AA′BB′, 2H), 8.88 (s, 1H), 9.89 (br s, 1H), 10.19 (br s, 1H), 10.49 (s, 1H); ¹³C NMR. (67.8 MHz, DMSO-d₆) δ 40.0, 115.0 (2C), 115.8 (2C), 124.1, 126.2, 126.5, 128.1 (2C), 128.2 (2C), 129.0 (2C), 130.1 (2C), 136.9, 138.4, 144.1, 148.6, 151.3, 159.1, 161.0, 165.9; IR (KBr, cm⁻¹) 621, 708, 754, 835, 1172, 1215, 1248, 1284, 1368, 1394, 1439, 1485, 1601, 1655, 3030, 3298.

3-5) TMD-366 (4y)

N-[3-Benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-3-methoxybenzamide (11y)

To a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int., 33, 477-485 (2001)) (800 mg, 2.75 mmol) in pyridine (10 mL) were successively added 4-(dimethylamino)pyridine (33.6 mg, 275 μmol) and m-anisoyl chloride (18) (773 μL, 5.50 mmol) at room temperature, and the mixture was heated with stirring at 50° C. for 22 hours. After cooling to room temperature, to the mixture was added water and the product was extracted with dichloromethane (×3). The combined organic extract was dried over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residual pyridine was azeotropically removed with toluene (×3). The residue was purified by column chromatography (silica gel 100 g, dichloromethane/ethyl acetate=9/1). The residue was recrystallized from ethyl acetate to give Compound fly (967 mg, 2.27 mmol, 82.5%) as a colorless solid. R_(f)=0.63 (dichloromethane/ethyl acetate=9/1); ¹H NMR (400 MHz, DMSO-d₆) δ 3.83 (s, 6H), 4.19 (s, 2H), 7.05-7.12 (AA′BB′, 2H), 7.14-7.28 (m, 6H), 7.42-7.49 (m, 2H), 7.53 (d, 1H, J=7.5 Hz), 8.06-8.12 (AA′BB′, 2H), 8.98 (s, 1H), 10.77 (s, 1H); ¹³C NMR (67.8 MHz, CDCl₃) δ 41.5, 55.3, 55.4, 112.5, 114.3 (2C), 118.6, 119.3, 126.7 (2C), 128.1, 128.55, 128.61 (2C), 128.5 (2C), 129.6, 135.0, 136.8, 137.7, 143.3, 149.2, 149.9, 159.8, 160.9, 165.7; IR (KBr, cm⁻¹) 700, 746, 833, 1022, 1040, 1117, 1179, 1254, 1300, 1325, 1373, 1416, 1441, 1501, 1607, 1655, 2936, 3265; Anal. Calcd. For C₂₆H₂₃N₃O₃: C, 73.39; H, 5.45; N, 9.88. Found: C, 73.55; H, 5.36; N, 9.86.

N-[3-Benzyl-5-(4-hydroxyphenyl)pyrazin-2-yl]-3-hydroxybenzamide (4y, TMD-366)

Under an argon atmosphere, to a solution of N-(3-benzyl-5-(4-methoxyphenyl)pyrazin-2-yl)-3-methoxybenzamide (11y) (300 mg, 705 μmol) in anhydrous dichloromethane (15 mL) was added boron tribromide (1.0 M dichloromethane solution, 3.53 mL, 3.53 mmol) at room temperature, and the mixture was heated to reflux for 19 hours. After cooling to room temperature, to this was added saturated aqueous sodium bicarbonate solution and the mixture was concentrated under reduced pressure using a rotary evaporator to remove dichloromethane. The solid was collected by filtration and dried in vacuo to give the crude product (343 mg) as an orange solid. The solid was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=2/3). The product was further recrystallized from ethyl acetate to give Compound 4y (TMD-366) (193 mg, 486 μmol, 68.9%) as a pale yellow solid. R_(f)=0.32 (n-hexane/ethyl acetate=1/2); ¹H NMR (400 MHz, DMSO-d₆) δ 4.16 (s, 2H), 6.86-6.92 (AA′BB′, 2H), 6.98-7.03 (m, 1H), 7.14-7.27 (m, 5H), 7.29-7.40 (m, 3H), 7.94-8.00 (AA′BB′, 2H), 8.90 (s, 1H), 9.78 (br s, 1H), 9.90 (br s, 1H), 10.65 (s, 1H); ¹³C NMR (67.8 MHz, DMSO-d₆) δ 114.8, 115.8 (2C), 118.4, 119.0, 126.2, 126.4, 128.1 (2C), 128.3 (2C), 129.0 (2C), 129.5, 135.0, 137.0, 138.3, 143.8, 148.9, 151.3, 157.4, 159.1, 166.3 (one carbon at the benzyl position was unobservable due to overlapping with the septet peak of DMSO); IR (KBr, cm⁻¹) 596, 683, 708, 748, 843, 1165, 1209, 1250, 1269, 1304, 1371, 1443, 1503, 1520, 1595, 1649, 3254.

3-6) TMD-368 (4z)

N-[3-Benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-6-methoxy-N-(6-methoxy-1-naphthoyl)-1-naphthamide (11z)

Under an argon atmosphere, 6-methoxy-1-naphthoic acid (synthesized by the process of J. D. Moseley and J. P. Gilday, Tetrahedron, 62, 4690-4697 (2006)) (1.20 g, 5.93 mmol) was dissolved in thionyl chloride (5.00 mL, 68.8 mmol) and the solution was heated to reflux for 3 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure to give the crude product of 6-methoxy-1-naphthoyl chloride (22) as a colorless oil. The product was used in the following reaction without further purification.

Under an argon atmosphere, to a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int., 33, 477-485 (2001)) (500 mg, 1.72 mmol) in pyridine (5 mL) were successively added 4-(dimethylamino)pyridine (21.0 mg, 172 μmol) and 6-methoxy-1-naphthoyl chloride (22) prepared above at room temperature, and the mixture was heated with stirring at 50° C. 18 hours. After cooling to room temperature, to the mixture was added water and the product was extracted with dichloromethane (×3). The combined organic extract was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residual pyridine was azeotropically removed with toluene (×3). The residue was successively purified twice by column chromatography (silica gel 50 g, dichloromethane/ethyl acetate=9/1, and silica gel 50 g, n-hexane/ethyl acetate=2/1) to give Compound 11z (775 mg, 1.17 mmol, <68.3%) as a brown foamy solid containing some impurities. R_(f)=0.21 (n-hexane/ethyl acetate=2/1); ¹H NMR (400 MHz, DMSO-d₆) δ 3.82 (s, 3H), 3.83 (s, 6H), 4.39 (s, 2H), 7.04-7.09 (AA′BB′, 2H), 7.15-7.23 (m, 6H), 7.26-7.31 (m, 1H), 7.34-7.41 (m, 4H), 7.63-7.69 (m, 2H), 7.75-7.80 (AA′BB′, 2H), 8.02-8.08 (m, 4H), 9.07 (s, 1H).

N-[3-Benzyl-5-(4-hydroxyphenyl)pyrazin-2-yl]-6-hydroxy-1-naphthamide (4z, TMD-368)

Under an argon atmosphere, to a solution of the crude product of N-[3-benzyl-5-(4-methoxyphenyl)pyrazin-2-yl]-6-methoxy-N-(6-methoxy-1-naphthoyl)-1-naphthamide (11z) (500 mg, <758 μmol) in anhydrous dichloromethane (15 mL) was added boron tribromide (1.0 M dichloromethane solution, 3.15 mL, 3.15 mmol) at room temperature, and the mixture was heated to reflux for 18 hours. After cooling to room temperature, to this was added saturated aqueous sodium bicarbonate solution. The solid in the suspension obtained during concentration under reduced pressure was collected by filtration and dried to give the crude product (294 mg, 657 μmol, <86.7%) as a brown solid. The product was recrystallized twice from ethyl acetate to give Compound 4z (TMD-368) (10.0 mg, 22.3 μmol, 2.9%) as a pale yellow solid. R_(f)=0.46 (n-hexane/ethyl acetate=1/2); ¹H NMR (400 MHz, DMSO-d₆) δ 4.32 (s, 2H), 6.85-6.94 (AA′BB′, 2H), 7.10-7.16 (m, 1H), 7.17-7.33 (m, 6H), 7.34-7.40 (m, 1H), 7.41-7.47 (m, 1H), 7.82-7.88 (m, 1H), 7.94-8.02 (AA′BB′, 2H), 8.04-8.09 (m, 1H), 8.92 (s, 1H), 9.91 (s, 2H), 10.83 (s, 1H).

Hereinafter, Compounds 3a, 3b and 3d to 3j in SYNTHESIS EXAMPLES described above are sometimes simply referred to as “coelenterazine analogues” and Compounds 4a to 4z as “coelenteramide analogues.”

Example 1

Preparation of Semi-Synthetic Aequorins for Substrate Specificity Analysis and Determination of Luminescence Activity

In preparing the following semi-synthetic aequorin, recombinant apoaequorin manufactured by Chisso Corporation was used. This recombinant apoaequorin was expressed and purified according to the method described in Inouye, S, and Hosoya. T. Biochem. Biophys. Res. Commun (2009) 386: 612-622.

(1) Preparation of Semi-Synthetic Aequorins

To 1 ml of 30 mM Tris-HCl (pH 7.6) containing 10 mM EDTA, 1 μl of 2-mercaptoethanol and 1.31 μg of the recombinant apoaequorin solution (manufactured by Chisso Corporation) were added and mixed. Subsequently, 1 μl of coelenterazine or its analogues dissolved in ethanol was added to the mixture. The mixture was allowed to stand at 4° C. for 18 hours to convert into semi-synthetic aequorins.

(2) Assay for Luminescence Activity

Specifically, the luminescence activity described above was assayed as follows. To 2 μl of a solution of semi-synthetic aequorin in each regeneration process was added 100 μl of 50 mM Tris-HCl (pH 7.6) containing 50 mM calcium chloride solution, whereby the luminescence reaction was triggered. The luminescence activity was measured for 10 seconds on a luminometer luminescencer-PSN AB2200 (manufactured by Atto Co., Ltd.) to obtain the maximum intensity (I_(max)) of luminescence activity. Also, the luminescence capacity of semi-synthetic aequorins was obtained by integrating for 10 seconds.

The results are summarized in TABLE 1 below. Semi-synthetic aequorins including coelenterazine analogues had sufficient luminescence intensities to detect the luminescence activity, though the maximum luminescence intensity was low.

Example 2

Measurement of Luminescence Patterns of Semi-Synthetic Aequorins and Determination of Half Decay Time

A solution of the regenerated semi-synthetic aequorin was diluted to 10-fold with 20 mM Tris-HCl (pH 7.6) containing 0.1% BSA (manufactured by Sigma, Inc.), 0.01 mM EDTA and 150 mM NaCl. The dilution was dispensed into a 96-well microplate (Nunc #236108) at 5 μl/well. The luminescence reaction was triggered by injecting 50 mM Tris-HCl (pH 7.6) containing 50 mM calcium chloride solution at 100 μl/well. The luminescence patterns for 60 seconds were measured to determine half decay time of the luminescence (a time period in which the luminescence becomes half of the maximum luminescence intensity).

The results are summarized in TABLE 1. The results reveal that semi-synthetic aequorins prepared from coelenterazine analogues had a longer half-decay time as compared to the half-decay time (0.81 second) of native aequorin prepared from coelenterazine; in particular, the half-decay time of semi-synthetic aequorins prepared from coelenterazine analogues 3a, 3e, 3f and 3j was markedly prolonged.

Example 3

Measurements of Luminescence Spectra of Semi-Synthetic Aequorins

In a quartz cell with light path length of 10 mm, 1 ml of 50 mM Tris-HCl (pH 7.6) containing 1 mM EDTA and 100 μl (100 μg protein) of a solution of the regenerated semi-synthetic aequorin were charged. Next, 100 μl of 50 mM Tris-HCl (pH 7.6) containing 0.1 ml of 10 mM calcium chloride solution was added thereto to start the luminescence reaction. The spectra were measured on a spectrofluorimeter (FP-6500, manufactured by Jasco Co., Ltd.) with the excitation light source turned off. The measurement conditions were bandwidth: 20 nm, response: 0.5 second, scan speed: 2000 nm/min and 22 to 25° C. The luminescence spectra measured were corrected.

The results are summarized in TABLE 1. The results reveal that the maximum emission peaks of semi-synthetic aequorins prepared from coelenterazine analogues 3a, 3e, 3f and 3h were shifted toward the longer wavelength by about 20 nm to 60 nm, by compared with the maximum emission peak at 472.5 nm from native aequorin prepared with coelenterazine. On the other hand, it became clear that the maximum emission peaks of semi-synthetic aequorins prepared from coelenterazine analogues 3b and 3j were shifted toward the shorter wavelength by about 15 nm to 25.5 nm.

Furthermore, as shown in FIG. 1, it became clear that semi-synthetic aequorins prepared from coelenterazine analogues had wider spectra.

TABLE 1 Luminescence Properties of Semi-Synthetic Aequorins by Addition of Calcium Ions Half Maximum Coelenterazine Luminescence Luminescence decay luminescence analogue activity capacity time wavelength (abbreviation) I_(max) (%) 10 sec. (%) (sec) λ_(max) (nm) Coelenterazine 100.0 100.0 0.81 472.5 (CTZ) 3a (TMD-296) 2.1 32.1 15.7 494.0 3b (TMD-282) 5.9 8.5 0.96 447.0 3d (TMD-276) 18.7 26.4 1.10 480.0 3e (TMD-277) 0.9 5.4 3.42 507.0 3f (TMD-278) 0.1 2.5 >60 515.0 3g (TMD-336) 0.02 0.15 — — 3h (TMD-281) 2.1 6.5 1.71 532.5 3i (TMD-337) 0.3 1.3 — — 3j (TMD-280) 4.2 67.0 16.8 457.5 (—) not measured (the activity is too low)

Example 4

Measurements of Fluorescence Spectra of Novel Fluorescent Proteins Formed from Semi-Synthetic Aequorins

The fluorescence spectra of novel fluorescent proteins formed by the Ca²⁺-triggered reaction from semi-synthetic aequorins in EXAMPLE 3 were measured at 25° C. in a quartz cell (10 mm light path length) using a Jasco FP-6500 spectrofluorometer (excitation wavelength: 330 nm, emission/excitation bandwidth: 3 nm; response: 0.5 sec, scan speed, 1000 nm/min). The fluorescence spectra measured were corrected.

The results are summarized in TABLE 2. It was revealed that all samples measured showed fluorescence intensity. The fluorescence spectra are shown in FIG. 2. The fluorescence spectra of fluorescent proteins obtained from coelenterazine analogues 3a, 3b, 3e, 3f, 3h and 3j were different from the emission spectra of semi-synthetic aequorins. Especially with coelenterazine analogues 3b, 3e and 3j, the emission spectra of semi-synthetic aequorins were markedly different from the fluorescence spectra of fluorescent proteins generated by the addition of calcium ions. This is the first example showing that the emission spectra are different from the fluorescence spectra, in spite of semi-synthetic aequorins and fluorescent proteins from the same coelenterazine analogues.

TABLE 2 Fluorescence spectra of fluorescent proteins Generated by Addition of Calcium Ions to Semi-Synthetic Aequorins Relative Maximum fluorescence fluorescence Coelenterazine analogue intensity wavelength (abbreviation) (rlu) λ_(max) (nm) Coelenterazine (CTZ) 63.3 473.0 3a (TMD-296) 118.1 501.5 3b (TMD-282) 10.3 580.0 3d (TMD-276) 61.8 482.5 3e (TMD-277) 28.0 468.5 3f (TMD-278) 38.5 525.0 3g (TMD-336) — — 3h (TMD-281) 58.7 537.0 3i (TMD-337) — — 3j (TMD-280) 13.3 580.0

Example 5

Preparation of Calcium Standard Solution

In 9 ml of 50 mM Tris-HCl (pH 7.6), 1 ml of 1 g/L calcium carbonate standard solution (manufactured by Wako Pure Chemicals) was diluted to prepare 10⁻³ M calcium carbonate solution. One milliliter of the resulting 10⁻³ M calcium carbonate solution was taken and added to 9 ml of 50 mM Tris-HCl (pH 7.6) to prepare 10⁻⁴ M calcium carbonate solution. Next, 3 ml of the resulting 10⁻⁴ M calcium carbonate solution was taken and added to 6 ml of 50 mM Tris-HCl (pH 7.6) to prepare 3×10⁻⁴ M calcium carbonate solution. One milliliter from the 10⁻⁴ M calcium carbonate solution obtained was added to 9 ml of 50 mM Tris-HCl (pH 7.6) to prepare 10⁻⁵ M calcium carbonate solution. Then, 3 ml of the resulting 10⁻⁵ M calcium carbonate solution was taken and added to 6 ml of 50 mM Tris-HCl (pH 7.6) to prepare 3×10⁻⁵ M calcium carbonate solution. A dilution series was prepared by successively repeating the procedures described above to give the 10⁻³ M to 10⁻⁸ M calcium standard solutions.

Example 6

Preparation of Semi-Synthetic Aequorins for the Detection of Calcium Concentration

In 5 ml of 50 mM Tris-HCl (pH 7.6) containing 10 mM DTT and 30 mM EDTA, 5 mg of recombinant apoaequorin (manufactured by Chisso Corporation) was dissolved and 100 μg of coelenterazine analogue dissolved in ethanol in an amount of 1.2-fold equivalent was added to the solution. The mixture was allowed to stand at 4° C. overnight to convert into semi-synthetic aequorin. The resulting semi-synthetic aequorin was concentrated using Amicon Ultra-4 (manufactured by Millipore, Inc., molecular weight cut-off: 10,000) to remove an excessive of coelenterazine analogue. The mixture was then washed 3 times with 3 ml of 30 mM Tris-HCl (pH 7.6) containing 0.05 mM EDTA to give the solution of semi-synthetic aequorin containing 0.05 mM EDTA. This semi-synthetic aequorin solution (2.5 mg/ml) was diluted with 20 mM Tris-HCl (pH 7.6) containing 0.1% BSA (manufactured by Sigma), 0.01 mM EDTA and 150 mM NaCl.

Example 7

Preparation of Calcium Standard Curve

The calcium standard solution prepared as above was dispensed into a 96-well microplate (Nunc #236108) at 50 μl/well and 10 μl of the diluted semi-synthetic aequorin solution was injected into 50 μl of various concentration of calcium standard solution. The luminescence intensity was measured for 60 seconds on a luminescence plate reader Centro LB960 (manufactured by Berthold) and expressed in terms of the maximum intensity (I_(max)) of luminescence. The luminescence intensity was measured on each semi-synthetic aequorin in the same procedures. Semi-synthetic aequorins for practically use were chosen by the maximum intensity (I_(max)) of luminescence and the calcium standard curve of semi-synthetic aequorin was prepared.

The results are shown in FIG. 3. As shown in FIG. 3, the calcium standard curve can be prepared using semi-synthetic aequorins prepared from coelenterazine analogues (3a, 3b, 3d, 3e, 3f, 3h and 3j) of the present invention, indicating that the photoprotein of the present invention can be used for the detection, quantification and the like of calcium ions.

Example 8

Determination of substrate specificity and luminescence activity of the 19 kDa protein from Oplophorus luciferase

The 19 kDa protein from Oplophorus luciferase was purified by the method described in Inouye, S, and Sasaki, S., Protein Express. Purif (2007) 56: 261-268 and provided for use.

After 1 μl of the 19 kDa protein (2.3 mg/ml) from Oplophorus luciferase containing 1 mM DTT was dissolved in 100 μl of 30 mM Tris-HCl (pH 7.6) containing 10 mM EDTA, 1 μl of a solution of coelenterazine or its analogue (1 μg/μl) in ethanol was added to the solution to start the luminescence reaction, and the luminescence activity was measured for 60 seconds on a luminometer luminescencer-PSN AB2200 (manufactured by Atto Co., Ltd.). The luminescence activity was determined by repeating the measurement described above 3 times and expressed in terms of the maximum luminescence intensity (I_(max)) of luminescence activity.

The results are shown in TABLE 3. Coelenterazine analogue was not a good substrate for Oplophorus luciferase.

TABLE 3 Luminescence activity of Oplophorus luciferase using coelenterazine analogues Coelenterazine analogue Luminescence (abbreviation) activity I_(max) (%) Coelenterazine (CTZ) 100.0 3a (TMD-296) 0.4 3b (TMD-282) 0.07 3d (TMD-276) 0.3 3e (TMD-277) 0.07 3f (TMD-278) 0.1 3g (TMD-336) 0.3 3h (TMD-281) 0.07 3i (TMD-337) 0.09 3j (TMD-280) 0.2

Example 9

Determination of Substrate Specificity and Luminescence Activity of Gaussia Luciferase

Gaussia luciferase was purified by the method described in Japanese Patent Application KOKAI No. 2008-099669 and provided for use. After 1 μl of Gaussia luciferase (0.024 mg/ml) was dissolved in 100 μl of phosphate buffered saline (manufactured by Sigma Inc.) containing 0.01% Tween 20 (manufactured by Sigma Inc.) and 10 mM EDTA, 1 μl of a solution of coelenterazine or its analogue (1 μg/μl) in ethanol was mixed with the solution to start the luminescence reaction. The luminescence activity was measured for 10 seconds on a luminometer luminescencer-PSN AB2200 (manufactured by Atto Co., Ltd.). The luminescence activity was determined by repeating the measurement described above 3 times and expressed in terms of the maximum luminescence intensity (I_(max)) of luminescence activity.

The results are shown in TABLE 4. Coelenterazine analogue was not a good substrate for Gaussia luciferase.

TABLE 4 luminescence activity of Gaussia luciferase using coelenterazine analogues Coelenterazine Luminescence analogue (abbreviation) activity I_(max) (%) Coelenterazine (CTZ) 100.0 3a (TMD-296) 0.00 3b (TMD-282) 0.01 3d (TMD-276) 0.00 3e (TMD-277) 0.00 3f (TMD-278) 0.00 3g (TMD-336) 0.00 3h (TMD-281) 0.00 3i (TMD-337) 0.00 3j (TMD-280) 0.01

Example 10

Determination of Substrate Specificity and Luminescence Activity of Renilla Luciferase

Renilla luciferase was purified by the method described in Inouye, S. & Shimomura, O. Biochem. Biophys. Res. Commun. (1997) 233: 349-353, and used for assay.

After 1 μl of Renilla luciferase (0.45 mg/ml) was dissolved in 100 μl of 30 mM Tris-HCl (pH 7.6) containing 10 mM EDTA, 1 μl of a solution of coelenterazine or its analogue (1 μg/μl) in ethanol was added to the solution to start the luminescence reaction. The luminescence activity was measured for 10 seconds on a luminometer luminescencer-PSN AB2200 (manufactured by Atto Co., Ltd.). The luminescence activity was determined by repeating the measurement of luminescence activity described above 3 times and expressed in terms of the maximum luminescence intensity (I_(max)) of luminescence activity.

The results are shown in TABLE 5. Coelenterazine analogue was not a good substrate for Renilla luciferase.

TABLE 5 Luminescence activity of Renilla luciferase using coelenterazine analogues Coelenterazine Luminescence analogue activity (abbreviation) I_(max) (%) Coelenterazine (CTZ) 100.0 3a (TMD-296) 0.00 3b (TMD-282) 0.00 3d (TMD-276) 0.00 3e (TMD-277) 0.00 3f (TMD-278) 0.00 3g (TMD-336) 0.00 3h (TMD-281) 0.00 3i (TMD-337) 0.00 3j (TMD-280) 0.03

Example 11

Preparation of Semi-Synthetic gFP from Coelenteramide Analogues and Apoaequorin

Semi-synthetic gFP was prepared from recombinant apoaequorin and coelenteramide analogues as follows. In 1 ml of 50 mM Tris-HC 1 (pH 7.6) containing 10 mM EDTA and 1 mM DTT, apoaequorin (0.2 mg) was mixed with 8 μl of a coelenteramide analogue (1 μg/μl in anhydrous methanol). The mixture was allowed to stand 4° C. for 16 hours to prepare semi-synthetic gFP-like protein (hereinafter sometimes simply referred to as “semi-synthetic gFP”).

Example 12

Preparation of Semi-Synthetic BFP from Coelenteramide Analogues and Apoaequorin

Semi-synthetic gFP was prepared from recombinant apoaequorin and coelenteramide analogues as follows. In 1 ml of 50 mM Tris-HCl (pH 7.6) containing 10 mM CaCl₂ and 1 mM DTT, apoaequorin (0.2 mg) was mixed with 8 μl of a coelenteramide analogue (1 μg/μl in anhydrous methanol). The mixture was allowed to stand at 4° C. for 16 hours to prepare semi-synthetic BFP-like protein (hereinafter sometimes simply referred to as “semi-synthetic BFP”).

Example 13

Measurement of the Fluorescence Spectra of Coelenteramide Analogues, Semi-Synthetic BFP and Semi-Synthetic gFP

The fluorescence spectra were determined as follows. For coelenteramide analogue alone, the fluorescence was measured according to the procedures for semi-synthetic gFP and semi-synthetic BFP described in EXAMPLES 11 and 12, except for in the absence of apoaequorin, using 1 ml of 50 mM Tris-HCl (pH 7.6) containing 10 mM EDTA and 1 mM DTT or 1 ml of 50 mM Tris-HCl (pH 7.6) containing 10 mM CaCl₂ and 1 mM DTT, in the final concentration of coelenteramide analogue adjusted to 8 μg/ml. The fluorescence spectra were measured at 25° C. in a quartz cell (10 mm light path length) using a Jasco FP-6500 spectrofluorometer (excitation wavelength: 337 nm, emission/excitation bandwidth: 3 nm; response: 0.5 sec, scan speed, 1000 nm/min).

The results are shown in TABLES 6 and 7. In addition, the charts of fluorescence spectra are shown in FIGS. 4 to 7.

Many of semi-synthetic BFPs and semi-synthetic gFPs prepared from coelenteramide analogues and apoaequorin showed much higher fluorescence intensities than that of coelenteramide analogue alone. Also, most of semi-synthetic BFPs and semi-synthetic gFPs had different fluorescence spectra from the fluorescence spectra of coelenteramide analogue alone.

TABLE 6 Fluorescence spectra of coelenteramide analogues and semi-synthetic gFPs in EDTA-containing buffer Coelenteramide (EDTA-containing Semi-synthetic gFP buffer) (EDTA-containing buffer) Maximum Maximum Coelenteramide fluorescence Fluorescence fluorescence Fluorescence analogue wavelength intensity wavelength intensity (abbreviation) λ_(max) (nm) (rlu) λ_(max) (nm) (rlu) Coelenteramide 458.0 4.6 482.5 165.2 (CTMD) 4a (TMD-344) 471.0 1.9 521.5 82.9 4b (TMD-343) 495.5 7.1 530.0 43.2 4c (TMD-347) 475.5 11.8 499.0 32.1 4d (TMD-338) 462.5 12.4 504.5 58.8 4e (TMD-339) 478.0 28.9 487.0 72.6 4f (TMD-340) 448.5 2.3 536.5 70.5 4g (TMD-345) 473.0 5.5 512.5 108.5 4h (TMD-342) 426.5 115.2 426.5 68.9 544.0 70.0 4i (TMD-346) 471.5 12.1 512.5 106.5 4j (TMD-341) 482.5 22.5 492.5 69.7 4k (TMD-373) 487.5 10.3 532.0 139.9 4l (TMD-374) 523.5 9.3 524.5 140.5 4m (TMD-375) 429.0 9.8 482.5 163.8 499.5 11.3 4n (TMD-376) N.D 485.5 151.5 4o (TMD-377) 482.5 2.1 485.0 3.4 4p (TMD-378) 476.0 5.3 523.0 21.1 4r (TMD-379) 481.0 10.3 468.0 176.4 4s (TMD-348) 457.5 1.9 460.0 106.4 4t (TMD-349) 480.5 11.8 482.5 22.0 4u (TMD-331) 440.5 0.7 494.5 11.4 4v (TMD-332) 484.0 1.4 491.0 3.6 4w (TMD-330) 451.0 1.3 487.0 54.6 4x (TMD-365) 449.0 1.3 404.0 15.1 492.5 23.1 4y (TMD-366) 456.0 1.3 492.0 44.8 4z (TMD-368) 409.5 20.2 492.5 246.3 N.D. not detected

TABLE 7 Fluorescence spectra of coelenteramide analogues and semi-synthetic BFPs in calcium ion-containing buffer Coelenteramide (Buffer containing Semi-synthetic BFP CaCl₂) (Buffer containing CaCl₂) Maximum Maximum Coelenteramide fluorescence Fluorescence fluorescence Fluorescence analogue wavelength wavelength wavelength wavelength (abbreviation) λ_(max) (nm) (rlu) λ_(max) (nm) (rlu) Coelenteramide 457.0 5.9 468.5 151.2 (CTMD) 4a (TMD-344) 467.5 2.0 507.5 148.9 4b (TMD-343) 494.5 9.4 544.5 52.7 4c (TMD-347) 471.0 12.4 492.5 25.6 4d (TMD-338) 463.5 12.9 487.0 98.3 4e (TMD-339) 478.0 28.6 492.5 85.6 4f (TMD-340) 447.0 2.2 527.0 96.4 4g (TMD-345) 470.5 6.1 501.5 195.7 4h (TMD-342) 426.5 101.2 427.0 153.3 4i (TMD-346) 468.0 11.8 494.0 80.0 4j (TMD-341) 481.0 22.4 489.0 100.5 4k (TMD-373) 491.0 9.7 538.5 148.2 4l (TMD-374) 523.0 8.8 468.0 63.5 4m (TMD-375) 438.5 7.3 457.5 182.4 502.0 11.6 4n (TMD-376) N.D 487.5 231.3 4o (TMD-377) 478.5 2.1 477.5 3.9 4p (TMD-378) 484.5 5.4 548.5 70.0 4r (TMD-379) 483.0 10.2 468.0 159.9 4s (TMD-348) 468.5 2.0 408.5 22.1 4t (TMD-349) 482.0 12.1 479.5 29.5 492.0 41.5 4u (TMD-331) 445.5 0.9 402.0 6.1 487.5 5.2 4v (TMD-332) 466.0 1.4 430.5 3.3 4w (TMD-330) 450.5 1.4 466.0 181.4 4x (TMD-365) 450.0 1.4 485.0 36.8 4y (TMD-366) 457.0 1.4 405.5 15.8 482.5 12.6 4z (TMD-368) 410.5 13.2 487.0 24.6 N.D. not detected

Example 14

Determination of the Luciferase Activity of Semi-Synthetic BFPs

To confirm that semi-synthetic BFPs prepared from coelenteramide analogues and apoaequorin, which are novel fluorescent proteins having luciferase activity, the luminescence reaction was performed in the presence of calcium ions, using coelenterazine as a light emitting substrate. After 5 μl (corresponding to 1 μg protein) of a solution of semi-synthetic BFP prepared in EXAMPLE 12 was added to 100 μl of 50 mM Tris-HCl (pH 7.6) containing 10 mM CaCl₂, 1 μl of a solution of coelenterazine (1 μg/μl) in ethanol was mixed with the solution to start the luminescence reaction. The luminescence activity was measured for 10 seconds on a luminometer luminescencer-PSN AB2200 (manufactured by Atto Co., Ltd.). The luminescence activity was determined by repeating the measurement of luminescence activity described above twice and expressed in terms of the maximum luminescence intensity (I_(max)) of luminescence activity. The results are shown in TABLE 8.

It became clear that semi-synthetic BFP has a sufficient luciferase activity. That is, semi-synthetic BFP was able to prepare various fluorescent proteins having the fluorescence activity and luciferase activity.

TABLE 8 Luciferase activity of semi-synthetic BFP using coelenterazine as a substrate Coelenteramide analogue Luciferase activity used to prepare of semi-synthetic semi-synthetic BFP BFP (%) CTMD 100.0 4a (TMD-344) 80.0 4b (TMD-343) 104.3 4c (TMD-347) 79.5 4d (TMD-338) 104.1 4e (TMD-339) 75.2 4f (TMD-340) 40.0 4g (TMD-345) 69.1 4h (TMD-342) 107.8 4i (TMD-346) 89.8 4j (TMD-341) 71.3 4k (TMD-373) 39.0 4l (TMD-374) 75.4 4m (TMD-375) 42.2 4n (TMD-376) 147.4 4o (TMD-377) 119.5 4p (TMD-378) 159.7 4r (TMD-379) 100.4 4s (TMD-348) 96.8 4t (TMD-349) 90.0 4u (TMD-331) 89.3 4v (TMD-332) 96.8 4w (TMD-330) 65.9 4x (TMD-365) 122.9 4y (TMD-366) 125.5 4z (TMD-368) 121.6 [Sequence Listing Free Text] [SEQ ID NO: 1]

This is the nucleotide sequence of native apoaequorin.

[SEQ ID NO: 2]

This is the amino acid sequence of native apoaequorin.

[SEQ ID NO: 3]

This shows the nucleotide sequence of native apoclytin-I.

[SEQ ID NO: 4]

This shows the amino acid sequence of native apoclytin-I.

[SEQ ID NO: 5]

This shows the nucleotide sequence of native apoclytin-II.

[SEQ ID NO: 6]

This shows the amino acid sequence of native apoclytin-II.

[SEQ ID NO: 7]

This shows the nucleotide sequence of native apomitrocomin.

[SEQ ID NO: 8]

This shows the amino acid sequence of native apomitrocomin.

[SEQ ID NO: 9]

This shows the nucleotide sequence of native apobelin.

[SEQ ID NO: 10]

This shows the amino acid sequence of native apobelin.

[SEQ ID NO: 11]

This shows the nucleotide sequence of native apobervoin.

[SEQ ID NO: 12]

This shows the amino acid sequence of native apobervoin. 

The invention claimed is:
 1. A compound represented by general formula (I) below:

wherein R³ is selected from the group consisting of a hydrogen atom, a bromine atom,

wherein each of R⁶, R⁷ and R⁸ independently represents a hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R⁶ and R⁸ may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R⁶ and R⁸, wherein the substituted or unsubstituted aryl formed by combining R⁶ and R⁸ together with the carbon atom bound to each R⁶ and R⁸ is selected from the group consisting of a naphthyl, an aminophenyl, and a nitrophenyl.
 2. The compound according to claim 1, wherein the compound is selected from the group consisting of:


3. The compound according to claim 1, wherein the compound is selected from the group consisting of:


4. A calcium-binding photoprotein comprising a peroxide of a compound represented by general formula (I) below:

wherein R³ is selected from the group consisting of a hydrogen atom, a bromine atom,

wherein each of R⁶, R⁷ and R⁸ independently represents a hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R⁶ and R⁸ may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R⁶ and R⁸, and an apoprotein of a calcium-binding photoprotein.
 5. A method for producing a calcium-binding photoprotein, which comprises contacting a compound represented by general formula (I) below:

wherein R³ is selected from the group consisting of a hydrogen atom, a bromine atom,

wherein each of R⁶, R⁷ and R⁸ independently represents a hydrogen atom, a substituted or unsubstituted alkyl having 1 to 6 carbon atoms, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; and R⁶ and R⁸ may be combined together to form a substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl with the carbon atom bound to each of R⁶ and R⁸, with an apoprotein of a calcium-binding photoprotein to obtain the calcium-binding photoprotein.
 6. A method for detecting or quantifying calcium ions, which comprises using the calcium-binding photoprotein according to claim
 4. 7. A method for analyzing a physiological function or enzyme activity, which comprises performing the bioluminescence resonance energy transfer (BRET) method using the calcium-binding photoprotein according to claim 4 as a donor protein.
 8. A method for producing a fluorescent protein, which comprises contacting the calcium-binding photoprotein according to claim 4 with a calcium ion or a divalent or trivalent ion replaceable for the calcium ion to obtain the fluorescent protein.
 9. The method according to claim 8, wherein the contact is carried out in the presence of a reducing agent.
 10. A compound represented by the following formula: 